RemoteFetcher
handles the details of fetching gems and gem information from a remote source.
SpecFetcher
handles metadata updates from remote gem repositories.
The UriFormatter
handles URIs from user-input and escaping.
uf = Gem::UriFormatter.new 'example.com' p uf.normalize #=> 'http://example.com'
Formats generated random numbers in many manners. When 'random/formatter'
is required, several methods are added to empty core module Random::Formatter
, making them available as Random’s instance and module methods.
Standard library SecureRandom
is also extended with the module, and the methods described below are available as a module methods in it.
Generate random hexadecimal strings:
require 'random/formatter' prng = Random.new prng.hex(10) #=> "52750b30ffbc7de3b362" prng.hex(10) #=> "92b15d6c8dc4beb5f559" prng.hex(13) #=> "39b290146bea6ce975c37cfc23" # or just Random.hex #=> "1aed0c631e41be7f77365415541052ee"
Generate random base64 strings:
prng.base64(10) #=> "EcmTPZwWRAozdA==" prng.base64(10) #=> "KO1nIU+p9DKxGg==" prng.base64(12) #=> "7kJSM/MzBJI+75j8" Random.base64(4) #=> "bsQ3fQ=="
Generate random binary strings:
prng.random_bytes(10) #=> "\016\t{\370g\310pbr\301" prng.random_bytes(10) #=> "\323U\030TO\234\357\020\a\337" Random.random_bytes(6) #=> "\xA1\xE6Lr\xC43"
Generate alphanumeric strings:
prng.alphanumeric(10) #=> "S8baxMJnPl" prng.alphanumeric(10) #=> "aOxAg8BAJe" Random.alphanumeric #=> "TmP9OsJHJLtaZYhP"
Generate UUIDs:
prng.uuid #=> "2d931510-d99f-494a-8c67-87feb05e1594" prng.uuid #=> "bad85eb9-0713-4da7-8d36-07a8e4b00eab" Random.uuid #=> "f14e0271-de96-45cc-8911-8910292a42cd"
All methods are available in the standard library SecureRandom
, too:
SecureRandom.hex #=> "05b45376a30c67238eb93b16499e50cf"
Generate a random number in the given range as Random
does
prng.random_number #=> 0.5816771641321361 prng.random_number(1000) #=> 485 prng.random_number(1..6) #=> 3 prng.rand #=> 0.5816771641321361 prng.rand(1000) #=> 485 prng.rand(1..6) #=> 3
A Float object represents a sometimes-inexact real number using the native architecture’s double-precision floating point representation.
Floating point has a different arithmetic and is an inexact number. So you should know its esoteric system. See following:
You can create a Float object explicitly with:
A floating-point literal.
You can convert certain objects to Floats with:
Method Float
.
First, what’s elsewhere. Class Float:
Inherits from class Numeric.
Here, class Float provides methods for:
finite?
: Returns whether self
is finite.
hash
: Returns the integer hash code for self
.
infinite?
: Returns whether self
is infinite.
nan?
: Returns whether self
is a NaN (not-a-number).
<
: Returns whether self
is less than the given value.
<=
: Returns whether self
is less than or equal to the given value.
<=>
: Returns a number indicating whether self
is less than, equal to, or greater than the given value.
==
(aliased as ===
and eql?
): Returns whether self
is equal to the given value.
>
: Returns whether self
is greater than the given value.
>=
: Returns whether self
is greater than or equal to the given value.
*
: Returns the product of self
and the given value.
**
: Returns the value of self
raised to the power of the given value.
+
: Returns the sum of self
and the given value.
-
: Returns the difference of self
and the given value.
/
: Returns the quotient of self
and the given value.
ceil
: Returns the smallest number greater than or equal to self
.
coerce
: Returns a 2-element array containing the given value converted to a Float and self
divmod
: Returns a 2-element array containing the quotient and remainder results of dividing self
by the given value.
fdiv
: Returns the Float
result of dividing self
by the given value.
floor
: Returns the greatest number smaller than or equal to self
.
next_float
: Returns the next-larger representable Float.
prev_float
: Returns the next-smaller representable Float.
quo
: Returns the quotient from dividing self
by the given value.
round
: Returns self
rounded to the nearest value, to a given precision.
to_i
(aliased as to_int
): Returns self
truncated to an Integer
.
to_s
(aliased as inspect
): Returns a string containing the place-value representation of self
in the given radix.
truncate
: Returns self
truncated to a given precision.
Continuation
objects are generated by Kernel#callcc
, after having +require+d continuation. They hold a return address and execution context, allowing a nonlocal return to the end of the callcc
block from anywhere within a program. Continuations are somewhat analogous to a structured version of C’s setjmp/longjmp
(although they contain more state, so you might consider them closer to threads).
For instance:
require "continuation" arr = [ "Freddie", "Herbie", "Ron", "Max", "Ringo" ] callcc{|cc| $cc = cc} puts(message = arr.shift) $cc.call unless message =~ /Max/
produces:
Freddie Herbie Ron Max
Also you can call callcc in other methods:
require "continuation" def g arr = [ "Freddie", "Herbie", "Ron", "Max", "Ringo" ] cc = callcc { |cc| cc } puts arr.shift return cc, arr.size end def f c, size = g c.call(c) if size > 1 end f
This (somewhat contrived) example allows the inner loop to abandon processing early:
require "continuation" callcc {|cont| for i in 0..4 print "#{i}: " for j in i*5...(i+1)*5 cont.call() if j == 17 printf "%3d", j end end } puts
produces:
0: 0 1 2 3 4 1: 5 6 7 8 9 2: 10 11 12 13 14 3: 15 16
A class which allows both internal and external iteration.
An Enumerator
can be created by the following methods.
Most methods have two forms: a block form where the contents are evaluated for each item in the enumeration, and a non-block form which returns a new Enumerator
wrapping the iteration.
enumerator = %w(one two three).each puts enumerator.class # => Enumerator enumerator.each_with_object("foo") do |item, obj| puts "#{obj}: #{item}" end # foo: one # foo: two # foo: three enum_with_obj = enumerator.each_with_object("foo") puts enum_with_obj.class # => Enumerator enum_with_obj.each do |item, obj| puts "#{obj}: #{item}" end # foo: one # foo: two # foo: three
This allows you to chain Enumerators together. For example, you can map a list’s elements to strings containing the index and the element as a string via:
puts %w[foo bar baz].map.with_index { |w, i| "#{i}:#{w}" } # => ["0:foo", "1:bar", "2:baz"] == External Iteration
An Enumerator
can also be used as an external iterator. For example, Enumerator#next
returns the next value of the iterator or raises StopIteration
if the Enumerator
is at the end.
e = [1,2,3].each # returns an enumerator object. puts e.next # => 1 puts e.next # => 2 puts e.next # => 3 puts e.next # raises StopIteration
next
, next_values
, peek
and peek_values
are the only methods which use external iteration (and Array#zip(Enumerable-not-Array)
which uses next
).
These methods do not affect other internal enumeration methods, unless the underlying iteration method itself has side-effect, e.g. IO#each_line
.
External iteration differs significantly from internal iteration due to using a Fiber:
- The Fiber adds some overhead compared to internal enumeration. - The stacktrace will only include the stack from the Enumerator, not above. - Fiber-local variables are *not* inherited inside the Enumerator Fiber, which instead starts with no Fiber-local variables. - Fiber storage variables *are* inherited and are designed to handle Enumerator Fibers. Assigning to a Fiber storage variable only affects the current Fiber, so if you want to change state in the caller Fiber of the Enumerator Fiber, you need to use an extra indirection (e.g., use some object in the Fiber storage variable and mutate some ivar of it).
Concretely:
Thread.current[:fiber_local] = 1 Fiber[:storage_var] = 1 e = Enumerator.new do |y| p Thread.current[:fiber_local] # for external iteration: nil, for internal iteration: 1 p Fiber[:storage_var] # => 1, inherited Fiber[:storage_var] += 1 y << 42 end p e.next # => 42 p Fiber[:storage_var] # => 1 (it ran in a different Fiber) e.each { p _1 } p Fiber[:storage_var] # => 2 (it ran in the same Fiber/"stack" as the current Fiber) == Convert External Iteration to Internal Iteration
You can use an external iterator to implement an internal iterator as follows:
def ext_each(e) while true begin vs = e.next_values rescue StopIteration return $!.result end y = yield(*vs) e.feed y end end o = Object.new def o.each puts yield puts yield(1) puts yield(1, 2) 3 end # use o.each as an internal iterator directly. puts o.each {|*x| puts x; [:b, *x] } # => [], [:b], [1], [:b, 1], [1, 2], [:b, 1, 2], 3 # convert o.each to an external iterator for # implementing an internal iterator. puts ext_each(o.to_enum) {|*x| puts x; [:b, *x] } # => [], [:b], [1], [:b, 1], [1, 2], [:b, 1, 2], 3
Raised to stop the iteration, in particular by Enumerator#next
. It is rescued by Kernel#loop
.
loop do puts "Hello" raise StopIteration puts "World" end puts "Done!"
produces:
Hello Done!
BigDecimal
provides arbitrary-precision floating point decimal arithmetic.
Ruby provides built-in support for arbitrary precision integer arithmetic.
For example:
42**13 #=> 1265437718438866624512
BigDecimal
provides similar support for very large or very accurate floating point numbers.
Decimal arithmetic is also useful for general calculation, because it provides the correct answers people expect–whereas normal binary floating point arithmetic often introduces subtle errors because of the conversion between base 10 and base 2.
For example, try:
sum = 0 10_000.times do sum = sum + 0.0001 end print sum #=> 0.9999999999999062
and contrast with the output from:
require 'bigdecimal' sum = BigDecimal("0") 10_000.times do sum = sum + BigDecimal("0.0001") end print sum #=> 0.1E1
Similarly:
(BigDecimal("1.2") - BigDecimal("1.0")) == BigDecimal("0.2") #=> true (1.2 - 1.0) == 0.2 #=> false
For a calculation using a BigDecimal and another value
, the precision of the result depends on the type of value
:
If value
is a Float, the precision is Float::DIG + 1.
If value
is a Rational, the precision is larger than Float::DIG + 1.
If value
is a BigDecimal, the precision is value
‘s precision in the internal representation, which is platform-dependent.
If value
is other object, the precision is determined by the result of +BigDecimal(value)+.
Because BigDecimal
is more accurate than normal binary floating point arithmetic, it requires some special values.
BigDecimal
sometimes needs to return infinity, for example if you divide a value by zero.
BigDecimal("1.0") / BigDecimal("0.0") #=> Infinity BigDecimal("-1.0") / BigDecimal("0.0") #=> -Infinity
You can represent infinite numbers to BigDecimal
using the strings 'Infinity'
, '+Infinity'
and '-Infinity'
(case-sensitive)
When a computation results in an undefined value, the special value NaN
(for ‘not a number’) is returned.
Example:
BigDecimal("0.0") / BigDecimal("0.0") #=> NaN
You can also create undefined values.
NaN is never considered to be the same as any other value, even NaN itself:
n = BigDecimal('NaN') n == 0.0 #=> false n == n #=> false
If a computation results in a value which is too small to be represented as a BigDecimal
within the currently specified limits of precision, zero must be returned.
If the value which is too small to be represented is negative, a BigDecimal
value of negative zero is returned.
BigDecimal("1.0") / BigDecimal("-Infinity") #=> -0.0
If the value is positive, a value of positive zero is returned.
BigDecimal("1.0") / BigDecimal("Infinity") #=> 0.0
(See BigDecimal.mode
for how to specify limits of precision.)
Note that -0.0
and 0.0
are considered to be the same for the purposes of comparison.
Note also that in mathematics, there is no particular concept of negative or positive zero; true mathematical zero has no sign.
When you require bigdecimal/util
, the to_d
method will be available on BigDecimal
and the native Integer
, Float
, Rational
, and String
classes:
require 'bigdecimal/util' 42.to_d # => 0.42e2 0.5.to_d # => 0.5e0 (2/3r).to_d(3) # => 0.667e0 "0.5".to_d # => 0.5e0
Copyright © 2002 by Shigeo Kobayashi <shigeo@tinyforest.gr.jp>.
BigDecimal
is released under the Ruby and 2-clause BSD licenses. See LICENSE.txt for details.
Maintained by mrkn <mrkn@mrkn.jp> and ruby-core members.
Documented by zzak <zachary@zacharyscott.net>, mathew <meta@pobox.com>, and many other contributors.
A rational number can be represented as a pair of integer numbers: a/b (b>0), where a is the numerator and b is the denominator. Integer
a equals rational a/1 mathematically.
You can create a Rational object explicitly with:
A rational literal.
You can convert certain objects to Rationals with:
Method Rational
.
Examples
Rational(1) #=> (1/1) Rational(2, 3) #=> (2/3) Rational(4, -6) #=> (-2/3) # Reduced. 3.to_r #=> (3/1) 2/3r #=> (2/3)
You can also create rational objects from floating-point numbers or strings.
Rational(0.3) #=> (5404319552844595/18014398509481984) Rational('0.3') #=> (3/10) Rational('2/3') #=> (2/3) 0.3.to_r #=> (5404319552844595/18014398509481984) '0.3'.to_r #=> (3/10) '2/3'.to_r #=> (2/3) 0.3.rationalize #=> (3/10)
A rational object is an exact number, which helps you to write programs without any rounding errors.
10.times.inject(0) {|t| t + 0.1 } #=> 0.9999999999999999 10.times.inject(0) {|t| t + Rational('0.1') } #=> (1/1)
However, when an expression includes an inexact component (numerical value or operation), it will produce an inexact result.
Rational(10) / 3 #=> (10/3) Rational(10) / 3.0 #=> 3.3333333333333335 Rational(-8) ** Rational(1, 3) #=> (1.0000000000000002+1.7320508075688772i)
Class Date provides methods for storing and manipulating calendar dates.
Consider using class Time instead of class Date if:
You need both dates and times; Date handles only dates.
You need only Gregorian dates (and not Julian dates); see Julian and Gregorian Calendars.
A Date object, once created, is immutable, and cannot be modified.
You can create a date for the current date, using Date.today
:
Date.today # => #<Date: 1999-12-31>
You can create a specific date from various combinations of arguments:
Date.new
takes integer year, month, and day-of-month:
Date.new(1999, 12, 31) # => #<Date: 1999-12-31>
Date.ordinal
takes integer year and day-of-year:
Date.ordinal(1999, 365) # => #<Date: 1999-12-31>
Date.jd
takes integer Julian day:
Date.jd(2451544) # => #<Date: 1999-12-31>
Date.commercial
takes integer commercial data (year, week, day-of-week):
Date.commercial(1999, 52, 5) # => #<Date: 1999-12-31>
Date.parse
takes a string, which it parses heuristically:
Date.parse('1999-12-31') # => #<Date: 1999-12-31> Date.parse('31-12-1999') # => #<Date: 1999-12-31> Date.parse('1999-365') # => #<Date: 1999-12-31> Date.parse('1999-W52-5') # => #<Date: 1999-12-31>
Date.strptime
takes a date string and a format string, then parses the date string according to the format string:
Date.strptime('1999-12-31', '%Y-%m-%d') # => #<Date: 1999-12-31> Date.strptime('31-12-1999', '%d-%m-%Y') # => #<Date: 1999-12-31> Date.strptime('1999-365', '%Y-%j') # => #<Date: 1999-12-31> Date.strptime('1999-W52-5', '%G-W%V-%u') # => #<Date: 1999-12-31> Date.strptime('1999 52 5', '%Y %U %w') # => #<Date: 1999-12-31> Date.strptime('1999 52 5', '%Y %W %u') # => #<Date: 1999-12-31> Date.strptime('fri31dec99', '%a%d%b%y') # => #<Date: 1999-12-31>
See also the specialized methods in “Specialized Format Strings” in Formats for Dates and Times
limit
Certain singleton methods in Date that parse string arguments also take optional keyword argument limit
, which can limit the length of the string argument.
When limit
is:
Non-negative: raises ArgumentError
if the string length is greater than limit.
Other numeric or nil
: ignores limit
.
Other non-numeric: raises TypeError
.
DateTime
A subclass of Date
that easily handles date, hour, minute, second, and offset.
DateTime
class is considered deprecated. Use Time
class.
DateTime
does not consider any leap seconds, does not track any summer time rules.
A DateTime
object is created with DateTime::new
, DateTime::jd
, DateTime::ordinal
, DateTime::commercial
, DateTime::parse
, DateTime::strptime
, DateTime::now
, Time#to_datetime
, etc.
require 'date' DateTime.new(2001,2,3,4,5,6) #=> #<DateTime: 2001-02-03T04:05:06+00:00 ...>
The last element of day, hour, minute, or second can be a fractional number. The fractional number’s precision is assumed at most nanosecond.
DateTime.new(2001,2,3.5) #=> #<DateTime: 2001-02-03T12:00:00+00:00 ...>
An optional argument, the offset, indicates the difference between the local time and UTC. For example, Rational(3,24)
represents ahead of 3 hours of UTC, Rational(-5,24)
represents behind of 5 hours of UTC. The offset should be -1 to +1, and its precision is assumed at most second. The default value is zero (equals to UTC).
DateTime.new(2001,2,3,4,5,6,Rational(3,24)) #=> #<DateTime: 2001-02-03T04:05:06+03:00 ...>
The offset also accepts string form:
DateTime.new(2001,2,3,4,5,6,'+03:00') #=> #<DateTime: 2001-02-03T04:05:06+03:00 ...>
An optional argument, the day of calendar reform (start
), denotes a Julian day number, which should be 2298874 to 2426355 or negative/positive infinity. The default value is Date::ITALY
(2299161=1582-10-15).
A DateTime
object has various methods. See each reference.
d = DateTime.parse('3rd Feb 2001 04:05:06+03:30') #=> #<DateTime: 2001-02-03T04:05:06+03:30 ...> d.hour #=> 4 d.min #=> 5 d.sec #=> 6 d.offset #=> (7/48) d.zone #=> "+03:30" d += Rational('1.5') #=> #<DateTime: 2001-02-04%16:05:06+03:30 ...> d = d.new_offset('+09:00') #=> #<DateTime: 2001-02-04%21:35:06+09:00 ...> d.strftime('%I:%M:%S %p') #=> "09:35:06 PM" d > DateTime.new(1999) #=> true
DateTime
and when should you use Time
? It’s a common misconception that William Shakespeare and Miguel de Cervantes died on the same day in history - so much so that UNESCO named April 23 as World Book Day because of this fact. However, because England hadn’t yet adopted the Gregorian Calendar Reform (and wouldn’t until 1752) their deaths are actually 10 days apart. Since Ruby’s Time
class implements a proleptic Gregorian calendar and has no concept of calendar reform there’s no way to express this with Time
objects. This is where DateTime
steps in:
shakespeare = DateTime.iso8601('1616-04-23', Date::ENGLAND) #=> Tue, 23 Apr 1616 00:00:00 +0000 cervantes = DateTime.iso8601('1616-04-23', Date::ITALY) #=> Sat, 23 Apr 1616 00:00:00 +0000
Already you can see something is weird - the days of the week are different. Taking this further:
cervantes == shakespeare #=> false (shakespeare - cervantes).to_i #=> 10
This shows that in fact they died 10 days apart (in reality 11 days since Cervantes died a day earlier but was buried on the 23rd). We can see the actual date of Shakespeare’s death by using the gregorian
method to convert it:
shakespeare.gregorian #=> Tue, 03 May 1616 00:00:00 +0000
So there’s an argument that all the celebrations that take place on the 23rd April in Stratford-upon-Avon are actually the wrong date since England is now using the Gregorian calendar. You can see why when we transition across the reform date boundary:
# start off with the anniversary of Shakespeare's birth in 1751 shakespeare = DateTime.iso8601('1751-04-23', Date::ENGLAND) #=> Tue, 23 Apr 1751 00:00:00 +0000 # add 366 days since 1752 is a leap year and April 23 is after February 29 shakespeare + 366 #=> Thu, 23 Apr 1752 00:00:00 +0000 # add another 365 days to take us to the anniversary in 1753 shakespeare + 366 + 365 #=> Fri, 04 May 1753 00:00:00 +0000
As you can see, if we’re accurately tracking the number of solar years since Shakespeare’s birthday then the correct anniversary date would be the 4th May and not the 23rd April.
So when should you use DateTime
in Ruby and when should you use Time
? Almost certainly you’ll want to use Time
since your app is probably dealing with current dates and times. However, if you need to deal with dates and times in a historical context you’ll want to use DateTime
to avoid making the same mistakes as UNESCO. If you also have to deal with timezones then best of luck - just bear in mind that you’ll probably be dealing with local solar times, since it wasn’t until the 19th century that the introduction of the railways necessitated the need for Standard Time and eventually timezones.
Pathname
represents the name of a file or directory on the filesystem, but not the file itself.
The pathname depends on the Operating System: Unix, Windows, etc. This library works with pathnames of local OS, however non-Unix pathnames are supported experimentally.
A Pathname
can be relative or absolute. It’s not until you try to reference the file that it even matters whether the file exists or not.
Pathname
is immutable. It has no method for destructive update.
The goal of this class is to manipulate file path information in a neater way than standard Ruby provides. The examples below demonstrate the difference.
All functionality from File
, FileTest
, and some from Dir
and FileUtils
is included, in an unsurprising way. It is essentially a facade for all of these, and more.
Pathname
require 'pathname' pn = Pathname.new("/usr/bin/ruby") size = pn.size # 27662 isdir = pn.directory? # false dir = pn.dirname # Pathname:/usr/bin base = pn.basename # Pathname:ruby dir, base = pn.split # [Pathname:/usr/bin, Pathname:ruby] data = pn.read pn.open { |f| _ } pn.each_line { |line| _ }
pn = "/usr/bin/ruby" size = File.size(pn) # 27662 isdir = File.directory?(pn) # false dir = File.dirname(pn) # "/usr/bin" base = File.basename(pn) # "ruby" dir, base = File.split(pn) # ["/usr/bin", "ruby"] data = File.read(pn) File.open(pn) { |f| _ } File.foreach(pn) { |line| _ }
p1 = Pathname.new("/usr/lib") # Pathname:/usr/lib p2 = p1 + "ruby/1.8" # Pathname:/usr/lib/ruby/1.8 p3 = p1.parent # Pathname:/usr p4 = p2.relative_path_from(p3) # Pathname:lib/ruby/1.8 pwd = Pathname.pwd # Pathname:/home/gavin pwd.absolute? # true p5 = Pathname.new "." # Pathname:. p5 = p5 + "music/../articles" # Pathname:music/../articles p5.cleanpath # Pathname:articles p5.realpath # Pathname:/home/gavin/articles p5.children # [Pathname:/home/gavin/articles/linux, ...]
These methods are effectively manipulating a String
, because that’s all a path is. None of these access the file system except for mountpoint?
, children
, each_child
, realdirpath
and realpath
.
+
File
status predicate methods These methods are a facade for FileTest:
File
property and manipulation methods These methods are a facade for File:
open
(*args, &block)
These methods are a facade for Dir:
each_entry
(&block)
IO
These methods are a facade for IO:
each_line
(*args, &block)
These methods are a mixture of Find
, FileUtils
, and others:
Method
documentation As the above section shows, most of the methods in Pathname
are facades. The documentation for these methods generally just says, for instance, “See FileTest.writable?
”, as you should be familiar with the original method anyway, and its documentation (e.g. through ri
) will contain more information. In some cases, a brief description will follow.
TCPServer
represents a TCP/IP server socket.
A simple TCP server may look like:
require 'socket' server = TCPServer.new 2000 # Server bind to port 2000 loop do client = server.accept # Wait for a client to connect client.puts "Hello !" client.puts "Time is #{Time.now}" client.close end
A more usable server (serving multiple clients):
require 'socket' server = TCPServer.new 2000 loop do Thread.start(server.accept) do |client| client.puts "Hello !" client.puts "Time is #{Time.now}" client.close end end
TCPSocket
represents a TCP/IP client socket.
A simple client may look like:
require 'socket' s = TCPSocket.new 'localhost', 2000 while line = s.gets # Read lines from socket puts line # and print them end s.close # close socket when done
This library provides three different ways to delegate method calls to an object. The easiest to use is SimpleDelegator
. Pass an object to the constructor and all methods supported by the object will be delegated. This object can be changed later.
Going a step further, the top level DelegateClass method allows you to easily setup delegation through class inheritance. This is considerably more flexible and thus probably the most common use for this library.
Finally, if you need full control over the delegation scheme, you can inherit from the abstract class Delegator
and customize as needed. (If you find yourself needing this control, have a look at Forwardable
which is also in the standard library. It may suit your needs better.)
SimpleDelegator’s implementation serves as a nice example of the use of Delegator:
require 'delegate' class SimpleDelegator < Delegator def __getobj__ @delegate_sd_obj # return object we are delegating to, required end def __setobj__(obj) @delegate_sd_obj = obj # change delegation object, # a feature we're providing end end
Be advised, RDoc
will not detect delegated methods.
A concrete implementation of Delegator
, this class provides the means to delegate all supported method calls to the object passed into the constructor and even to change the object being delegated to at a later time with __setobj__
.
class User def born_on Date.new(1989, 9, 10) end end require 'delegate' class UserDecorator < SimpleDelegator def birth_year born_on.year end end decorated_user = UserDecorator.new(User.new) decorated_user.birth_year #=> 1989 decorated_user.__getobj__ #=> #<User: ...>
A SimpleDelegator
instance can take advantage of the fact that SimpleDelegator
is a subclass of Delegator
to call super
to have methods called on the object being delegated to.
class SuperArray < SimpleDelegator def [](*args) super + 1 end end SuperArray.new([1])[0] #=> 2
Here’s a simple example that takes advantage of the fact that SimpleDelegator’s delegation object can be changed at any time.
class Stats def initialize @source = SimpleDelegator.new([]) end def stats(records) @source.__setobj__(records) "Elements: #{@source.size}\n" + " Non-Nil: #{@source.compact.size}\n" + " Unique: #{@source.uniq.size}\n" end end s = Stats.new puts s.stats(%w{James Edward Gray II}) puts puts s.stats([1, 2, 3, nil, 4, 5, 1, 2])
Prints:
Elements: 4 Non-Nil: 4 Unique: 4 Elements: 8 Non-Nil: 7 Unique: 6
Class Data provides a convenient way to define simple classes for value-alike objects.
The simplest example of usage:
Measure = Data.define(:amount, :unit) # Positional arguments constructor is provided distance = Measure.new(100, 'km') #=> #<data Measure amount=100, unit="km"> # Keyword arguments constructor is provided weight = Measure.new(amount: 50, unit: 'kg') #=> #<data Measure amount=50, unit="kg"> # Alternative form to construct an object: speed = Measure[10, 'mPh'] #=> #<data Measure amount=10, unit="mPh"> # Works with keyword arguments, too: area = Measure[amount: 1.5, unit: 'm^2'] #=> #<data Measure amount=1.5, unit="m^2"> # Argument accessors are provided: distance.amount #=> 100 distance.unit #=> "km"
Constructed object also has a reasonable definitions of ==
operator, to_h
hash conversion, and deconstruct
/#deconstruct_keys to be used in pattern matching.
::define
method accepts an optional block and evaluates it in the context of the newly defined class. That allows to define additional methods:
Measure = Data.define(:amount, :unit) do def <=>(other) return unless other.is_a?(self.class) && other.unit == unit amount <=> other.amount end include Comparable end Measure[3, 'm'] < Measure[5, 'm'] #=> true Measure[3, 'm'] < Measure[5, 'kg'] # comparison of Measure with Measure failed (ArgumentError)
Data
provides no member writers, or enumerators: it is meant to be a storage for immutable atomic values. But note that if some of data members is of a mutable class, Data
does no additional immutability enforcement:
Event = Data.define(:time, :weekdays) event = Event.new('18:00', %w[Tue Wed Fri]) #=> #<data Event time="18:00", weekdays=["Tue", "Wed", "Fri"]> # There is no #time= or #weekdays= accessors, but changes are # still possible: event.weekdays << 'Sat' event #=> #<data Event time="18:00", weekdays=["Tue", "Wed", "Fri", "Sat"]>
See also Struct
, which is a similar concept, but has more container-alike API, allowing to change contents of the object and enumerate it.
The Etc
module provides access to information typically stored in files in the /etc
directory on Unix systems.
The information accessible consists of the information found in the /etc/passwd
and /etc/group
files, plus information about the system’s temporary directory (/tmp
) and configuration directory (/etc
).
The Etc
module provides a more reliable way to access information about the logged in user than environment variables such as +$USER+.
require 'etc' login = Etc.getlogin info = Etc.getpwnam(login) username = info.gecos.split(/,/).first puts "Hello #{username}, I see your login name is #{login}"
Note that the methods provided by this module are not always secure. It should be used for informational purposes, and not for security.
All operations defined in this module are class methods, so that you can include the Etc
module into your class.
Psych
is a YAML
parser and emitter. Psych
leverages libyaml [Home page: pyyaml.org/wiki/LibYAML] or [git repo: github.com/yaml/libyaml] for its YAML
parsing and emitting capabilities. In addition to wrapping libyaml, Psych
also knows how to serialize and de-serialize most Ruby objects to and from the YAML
format.
YAML
RIGHT NOW! # Parse some YAML Psych.load("--- foo") # => "foo" # Emit some YAML Psych.dump("foo") # => "--- foo\n...\n" { :a => 'b'}.to_yaml # => "---\n:a: b\n"
Got more time on your hands? Keep on reading!
YAML
Parsing Psych
provides a range of interfaces for parsing a YAML
document ranging from low level to high level, depending on your parsing needs. At the lowest level, is an event based parser. Mid level is access to the raw YAML
AST, and at the highest level is the ability to unmarshal YAML
to Ruby objects.
YAML
Emitting Psych
provides a range of interfaces ranging from low to high level for producing YAML
documents. Very similar to the YAML
parsing interfaces, Psych
provides at the lowest level, an event based system, mid-level is building a YAML
AST, and the highest level is converting a Ruby object straight to a YAML
document.
The high level YAML
parser provided by Psych
simply takes YAML
as input and returns a Ruby data structure. For information on using the high level parser see Psych.load
Psych.safe_load("--- a") # => 'a' Psych.safe_load("---\n - a\n - b") # => ['a', 'b'] # From a trusted string: Psych.load("--- !ruby/range\nbegin: 0\nend: 42\nexcl: false\n") # => 0..42
Psych.safe_load_file("data.yml", permitted_classes: [Date]) Psych.load_file("trusted_database.yml")
Exception
handling begin # The second argument changes only the exception contents Psych.parse("--- `", "file.txt") rescue Psych::SyntaxError => ex ex.file # => 'file.txt' ex.message # => "(file.txt): found character that cannot start any token" end
The high level emitter has the easiest interface. Psych
simply takes a Ruby data structure and converts it to a YAML
document. See Psych.dump
for more information on dumping a Ruby data structure.
# Dump an array, get back a YAML string Psych.dump(['a', 'b']) # => "---\n- a\n- b\n" # Dump an array to an IO object Psych.dump(['a', 'b'], StringIO.new) # => #<StringIO:0x000001009d0890> # Dump an array with indentation set Psych.dump(['a', ['b']], :indentation => 3) # => "---\n- a\n- - b\n" # Dump an array to an IO with indentation set Psych.dump(['a', ['b']], StringIO.new, :indentation => 3)
Currently there is no direct API for dumping Ruby structure to file:
File.open('database.yml', 'w') do |file| file.write(Psych.dump(['a', 'b'])) end
Psych
provides access to an AST produced from parsing a YAML
document. This tree is built using the Psych::Parser
and Psych::TreeBuilder
. The AST can be examined and manipulated freely. Please see Psych::parse_stream
, Psych::Nodes
, and Psych::Nodes::Node
for more information on dealing with YAML
syntax trees.
# Returns Psych::Nodes::Stream Psych.parse_stream("---\n - a\n - b") # Returns Psych::Nodes::Document Psych.parse("---\n - a\n - b")
# Returns Psych::Nodes::Stream Psych.parse_stream(File.read('database.yml')) # Returns Psych::Nodes::Document Psych.parse_file('database.yml')
Exception
handling begin # The second argument changes only the exception contents Psych.parse("--- `", "file.txt") rescue Psych::SyntaxError => ex ex.file # => 'file.txt' ex.message # => "(file.txt): found character that cannot start any token" end
At the mid level is building an AST. This AST is exactly the same as the AST used when parsing a YAML
document. Users can build an AST by hand and the AST knows how to emit itself as a YAML
document. See Psych::Nodes
, Psych::Nodes::Node
, and Psych::TreeBuilder
for more information on building a YAML
AST.
# We need Psych::Nodes::Stream (not Psych::Nodes::Document) stream = Psych.parse_stream("---\n - a\n - b") stream.to_yaml # => "---\n- a\n- b\n"
# We need Psych::Nodes::Stream (not Psych::Nodes::Document) stream = Psych.parse_stream(File.read('database.yml')) File.open('database.yml', 'w') do |file| file.write(stream.to_yaml) end
The lowest level parser should be used when the YAML
input is already known, and the developer does not want to pay the price of building an AST or automatic detection and conversion to Ruby objects. See Psych::Parser
for more information on using the event based parser.
Psych::Nodes::Stream
structure parser = Psych::Parser.new(TreeBuilder.new) # => #<Psych::Parser> parser = Psych.parser # it's an alias for the above parser.parse("---\n - a\n - b") # => #<Psych::Parser> parser.handler # => #<Psych::TreeBuilder> parser.handler.root # => #<Psych::Nodes::Stream>
recorder = Psych::Handlers::Recorder.new parser = Psych::Parser.new(recorder) parser.parse("---\n - a\n - b") recorder.events # => [list of [event, args] lists] # event is one of: Psych::Handler::EVENTS # args are the arguments passed to the event
The lowest level emitter is an event based system. Events are sent to a Psych::Emitter
object. That object knows how to convert the events to a YAML
document. This interface should be used when document format is known in advance or speed is a concern. See Psych::Emitter
for more information.
Psych.parser.parse("--- a") # => #<Psych::Parser> parser.handler.first # => #<Psych::Nodes::Stream> parser.handler.first.to_ruby # => ["a"] parser.handler.root.first # => #<Psych::Nodes::Document> parser.handler.root.first.to_ruby # => "a" # You can instantiate an Emitter manually Psych::Visitors::ToRuby.new.accept(parser.handler.root.first) # => "a"
define UnicodeNormalize module here so that we don’t have to look it up
The marshaling library converts collections of Ruby objects into a byte stream, allowing them to be stored outside the currently active script. This data may subsequently be read and the original objects reconstituted.
Marshaled data has major and minor version numbers stored along with the object information. In normal use, marshaling can only load data written with the same major version number and an equal or lower minor version number. If Ruby’s “verbose” flag is set (normally using -d, -v, -w, or –verbose) the major and minor numbers must match exactly. Marshal
versioning is independent of Ruby’s version numbers. You can extract the version by reading the first two bytes of marshaled data.
str = Marshal.dump("thing") RUBY_VERSION #=> "1.9.0" str[0].ord #=> 4 str[1].ord #=> 8
Some objects cannot be dumped: if the objects to be dumped include bindings, procedure or method objects, instances of class IO
, or singleton objects, a TypeError
will be raised.
If your class has special serialization needs (for example, if you want to serialize in some specific format), or if it contains objects that would otherwise not be serializable, you can implement your own serialization strategy.
There are two methods of doing this, your object can define either marshal_dump and marshal_load or _dump and _load. marshal_dump will take precedence over _dump if both are defined. marshal_dump may result in smaller Marshal
strings.
By design, Marshal.load
can deserialize almost any class loaded into the Ruby process. In many cases this can lead to remote code execution if the Marshal
data is loaded from an untrusted source.
As a result, Marshal.load
is not suitable as a general purpose serialization format and you should never unmarshal user supplied input or other untrusted data.
If you need to deserialize untrusted data, use JSON
or another serialization format that is only able to load simple, ‘primitive’ types such as String
, Array
, Hash
, etc. Never allow user input to specify arbitrary types to deserialize into.
When dumping an object the method marshal_dump will be called. marshal_dump must return a result containing the information necessary for marshal_load to reconstitute the object. The result can be any object.
When loading an object dumped using marshal_dump the object is first allocated then marshal_load is called with the result from marshal_dump. marshal_load must recreate the object from the information in the result.
Example:
class MyObj def initialize name, version, data @name = name @version = version @data = data end def marshal_dump [@name, @version] end def marshal_load array @name, @version = array end end
Use _dump and _load when you need to allocate the object you’re restoring yourself.
When dumping an object the instance method _dump is called with an Integer
which indicates the maximum depth of objects to dump (a value of -1 implies that you should disable depth checking). _dump must return a String
containing the information necessary to reconstitute the object.
The class method _load should take a String
and use it to return an object of the same class.
Example:
class MyObj def initialize name, version, data @name = name @version = version @data = data end def _dump level [@name, @version].join ':' end def self._load args new(*args.split(':')) end end
Since Marshal.dump
outputs a string you can have _dump return a Marshal
string which is Marshal.loaded in _load for complex objects.
Class for representing HTTP method PATCH:
require 'net/http' uri = URI('http://example.com') hostname = uri.hostname # => "example.com" uri.path = '/posts' req = Net::HTTP::Patch.new(uri) # => #<Net::HTTP::Patch PATCH> req.body = '{"title": "foo","body": "bar","userId": 1}' req.content_type = 'application/json' res = Net::HTTP.start(hostname) do |http| http.request(req) end
Properties:
Request body: yes.
Response body: yes.
Safe: no.
Idempotent: no.
Cacheable: no.
Related:
Net::HTTP#patch
: sends PATCH
request, returns response object.