Results for: "remove_const"

Gem::DependencyInstaller

Installs a gem along with all its dependencies from local and remote gems.

Gem::ConflictError

Raised when there are conflicting gem specs loaded

Gem::UninstallError

Raised when removing a gem with the uninstall command fails

Gem::InstallError

No documentation available

Gem::InvalidSpecificationException

Potentially raised when a specification is validated.

Gem::Installer

The installer installs the files contained in the .gem into the Gem.home.

Gem::Installer does the work of putting files in all the right places on the filesystem including unpacking the gem into its gem dir, installing the gemspec in the specifications dir, storing the cached gem in the cache dir, and installing either wrappers or symlinks for executables.

The installer invokes pre and post install hooks. Hooks can be added either through a rubygems_plugin.rb file in an installed gem or via a rubygems/defaults/#{RUBY_ENGINE}.rb or rubygems/defaults/operating_system.rb file. See Gem.pre_install and Gem.post_install for details.

Gem::StubSpecification

Gem::StubSpecification reads the stub: line from the gemspec. This prevents us having to eval the entire gemspec in order to find out certain information.

Gem::Uninstaller

An Uninstaller.

The uninstaller fires pre and post uninstall hooks. Hooks can be added either through a rubygems_plugin.rb file in an installed gem or via a rubygems/defaults/#{RUBY_ENGINE}.rb or rubygems/defaults/operating_system.rb file. See Gem.pre_uninstall and Gem.post_uninstall for details.

URI::InvalidComponentError

Not a URI component.

Digest::Instance

This module provides instance methods for a digest implementation object to calculate message digest values.

OpenSSL::ExtConfig

This module contains configuration information about the SSL extension, for example if socket support is enabled, or the host name TLS extension is enabled. Constants in this module will always be defined, but contain true or false values depending on the configuration of your OpenSSL installation.

CGI::QueryExtension

Mixin module that provides the following:

  1. Access to the CGI environment variables as methods. See documentation to the CGI class for a list of these variables. The methods are exposed by removing the leading HTTP_ (if it exists) and downcasing the name. For example, auth_type will return the environment variable AUTH_TYPE, and accept will return the value for HTTP_ACCEPT.

  2. Access to cookies, including the cookies attribute.

  3. Access to parameters, including the params attribute, and overloading [] to perform parameter value lookup by key.

  4. The initialize_query method, for initializing the above mechanisms, handling multipart forms, and allowing the class to be used in “offline” mode.

CGI::HtmlExtension

Mixin module providing HTML generation methods.

For example,

cgi.a("http://www.example.com") { "Example" }
  # => "<A HREF=\"http://www.example.com\">Example</A>"

Modules Html3, Html4, etc., contain more basic HTML-generation methods (#title, #h1, etc.).

See class CGI for a detailed example.

MakeMakefile::RbConfig

No documentation available

Net::HTTPExceptions

Net::HTTP exception class. You cannot use Net::HTTPExceptions directly; instead, you must use its subclasses.

OptionParser::Completion

Keyword completion module. This allows partial arguments to be specified and resolved against a list of acceptable values.

Complex

A complex number can be represented as a paired real number with imaginary unit; a+bi. Where a is real part, b is imaginary part and i is imaginary unit. Real a equals complex a+0i mathematically.

You can create a Complex object explicitly with:

You can convert certain objects to Complex objects with:

Complex object can be created as literal, and also by using Kernel#Complex, Complex::rect, Complex::polar or to_c method.

2+1i                 #=> (2+1i)
Complex(1)           #=> (1+0i)
Complex(2, 3)        #=> (2+3i)
Complex.polar(2, 3)  #=> (-1.9799849932008908+0.2822400161197344i)
3.to_c               #=> (3+0i)

You can also create complex object from floating-point numbers or strings.

Complex(0.3)         #=> (0.3+0i)
Complex('0.3-0.5i')  #=> (0.3-0.5i)
Complex('2/3+3/4i')  #=> ((2/3)+(3/4)*i)
Complex('1@2')       #=> (-0.4161468365471424+0.9092974268256817i)

0.3.to_c             #=> (0.3+0i)
'0.3-0.5i'.to_c      #=> (0.3-0.5i)
'2/3+3/4i'.to_c      #=> ((2/3)+(3/4)*i)
'1@2'.to_c           #=> (-0.4161468365471424+0.9092974268256817i)

A complex object is either an exact or an inexact number.

Complex(1, 1) / 2    #=> ((1/2)+(1/2)*i)
Complex(1, 1) / 2.0  #=> (0.5+0.5i)

String

A String object has an arbitrary sequence of bytes, typically representing text or binary data. A String object may be created using String::new or as literals.

String objects differ from Symbol objects in that Symbol objects are designed to be used as identifiers, instead of text or data.

You can create a String object explicitly with:

You can convert certain objects to Strings with:

Some String methods modify self. Typically, a method whose name ends with ! modifies self and returns self; often a similarly named method (without the !) returns a new string.

In general, if there exist both bang and non-bang version of method, the bang! mutates and the non-bang! does not. However, a method without a bang can also mutate, such as String#replace.

Substitution Methods

These methods perform substitutions:

Each of these methods takes:

The examples in this section mostly use methods String#sub and String#gsub; the principles illustrated apply to all four substitution methods.

Argument pattern

Argument pattern is commonly a regular expression:

s = 'hello'
s.sub(/[aeiou]/, '*')  # => "h*llo"
s.gsub(/[aeiou]/, '*') # => "h*ll*"
s.gsub(/[aeiou]/, '')  # => "hll"
s.sub(/ell/, 'al')     # => "halo"
s.gsub(/xyzzy/, '*')   # => "hello"
'THX1138'.gsub(/\d+/, '00') # => "THX00"

When pattern is a string, all its characters are treated as ordinary characters (not as regexp special characters):

'THX1138'.gsub('\d+', '00') # => "THX1138"

String replacement

If replacement is a string, that string will determine the replacing string that is to be substituted for the matched text.

Each of the examples above uses a simple string as the replacing string.

String replacement may contain back-references to the pattern’s captures:

See regexp.rdoc for details.

Note that within the string replacement, a character combination such as $& is treated as ordinary text, and not as a special match variable. However, you may refer to some special match variables using these combinations:

See regexp.rdoc for details.

Note that \\ is interpreted as an escape, i.e., a single backslash.

Note also that a string literal consumes backslashes. See String Literals for details about string literals.

A back-reference is typically preceded by an additional backslash. For example, if you want to write a back-reference \& in replacement with a double-quoted string literal, you need to write "..\\&..".

If you want to write a non-back-reference string \& in replacement, you need first to escape the backslash to prevent this method from interpreting it as a back-reference, and then you need to escape the backslashes again to prevent a string literal from consuming them: "..\\\\&..".

You may want to use the block form to avoid a lot of backslashes.

Hash replacement

If argument replacement is a hash, and pattern matches one of its keys, the replacing string is the value for that key:

h = {'foo' => 'bar', 'baz' => 'bat'}
'food'.sub('foo', h) # => "bard"

Note that a symbol key does not match:

h = {foo: 'bar', baz: 'bat'}
'food'.sub('foo', h) # => "d"

Block

In the block form, the current match string is passed to the block; the block’s return value becomes the replacing string:

 s = '@'
'1234'.gsub(/\d/) {|match| s.succ! } # => "ABCD"

Special match variables such as $1, $2, $`, $&, and $' are set appropriately.

What’s Here

First, what’s elsewhere. Class String:

Here, class String provides methods that are useful for:

Methods for Creating a String

Methods for a Frozen/Unfrozen String

Methods for Querying

Counts

Substrings

Encodings

Other

Methods for Comparing

Methods for Modifying a String

Each of these methods modifies self.

Insertion

Substitution

Casing

Encoding

Deletion

Methods for Converting to New String

Each of these methods returns a new String based on self, often just a modified copy of self.

Extension

Encoding

Substitution

Casing

Deletion

Duplication

Methods for Converting to Non-String

Each of these methods converts the contents of self to a non-String.

Characters, Bytes, and Clusters

Splitting

Matching

Numerics

Strings and Symbols

Methods for Iterating

Encoding

An Encoding instance represents a character encoding usable in Ruby. It is defined as a constant under the Encoding namespace. It has a name and optionally, aliases:

Encoding::ISO_8859_1.name
#=> "ISO-8859-1"

Encoding::ISO_8859_1.names
#=> ["ISO-8859-1", "ISO8859-1"]

Ruby methods dealing with encodings return or accept Encoding instances as arguments (when a method accepts an Encoding instance as an argument, it can be passed an Encoding name or alias instead).

"some string".encoding
#=> #<Encoding:UTF-8>

string = "some string".encode(Encoding::ISO_8859_1)
#=> "some string"
string.encoding
#=> #<Encoding:ISO-8859-1>

"some string".encode "ISO-8859-1"
#=> "some string"

Encoding::ASCII_8BIT is a special encoding that is usually used for a byte string, not a character string. But as the name insists, its characters in the range of ASCII are considered as ASCII characters. This is useful when you use ASCII-8BIT characters with other ASCII compatible characters.

Changing an encoding

The associated Encoding of a String can be changed in two different ways.

First, it is possible to set the Encoding of a string to a new Encoding without changing the internal byte representation of the string, with String#force_encoding. This is how you can tell Ruby the correct encoding of a string.

string
#=> "R\xC3\xA9sum\xC3\xA9"
string.encoding
#=> #<Encoding:ISO-8859-1>
string.force_encoding(Encoding::UTF_8)
#=> "R\u00E9sum\u00E9"

Second, it is possible to transcode a string, i.e. translate its internal byte representation to another encoding. Its associated encoding is also set to the other encoding. See String#encode for the various forms of transcoding, and the Encoding::Converter class for additional control over the transcoding process.

string
#=> "R\u00E9sum\u00E9"
string.encoding
#=> #<Encoding:UTF-8>
string = string.encode!(Encoding::ISO_8859_1)
#=> "R\xE9sum\xE9"
string.encoding
#=> #<Encoding::ISO-8859-1>

Script encoding

All Ruby script code has an associated Encoding which any String literal created in the source code will be associated to.

The default script encoding is Encoding::UTF_8 after v2.0, but it can be changed by a magic comment on the first line of the source code file (or second line, if there is a shebang line on the first). The comment must contain the word coding or encoding, followed by a colon, space and the Encoding name or alias:

# encoding: UTF-8

"some string".encoding
#=> #<Encoding:UTF-8>

The __ENCODING__ keyword returns the script encoding of the file which the keyword is written:

# encoding: ISO-8859-1

__ENCODING__
#=> #<Encoding:ISO-8859-1>

ruby -K will change the default locale encoding, but this is not recommended. Ruby source files should declare its script encoding by a magic comment even when they only depend on US-ASCII strings or regular expressions.

Locale encoding

The default encoding of the environment. Usually derived from locale.

see Encoding.locale_charmap, Encoding.find(‘locale’)

Filesystem encoding

The default encoding of strings from the filesystem of the environment. This is used for strings of file names or paths.

see Encoding.find(‘filesystem’)

External encoding

Each IO object has an external encoding which indicates the encoding that Ruby will use to read its data. By default Ruby sets the external encoding of an IO object to the default external encoding. The default external encoding is set by locale encoding or the interpreter -E option. Encoding.default_external returns the current value of the external encoding.

ENV["LANG"]
#=> "UTF-8"
Encoding.default_external
#=> #<Encoding:UTF-8>

$ ruby -E ISO-8859-1 -e "p Encoding.default_external"
#<Encoding:ISO-8859-1>

$ LANG=C ruby -e 'p Encoding.default_external'
#<Encoding:US-ASCII>

The default external encoding may also be set through Encoding.default_external=, but you should not do this as strings created before and after the change will have inconsistent encodings. Instead use ruby -E to invoke ruby with the correct external encoding.

When you know that the actual encoding of the data of an IO object is not the default external encoding, you can reset its external encoding with IO#set_encoding or set it at IO object creation (see IO.new options).

Internal encoding

To process the data of an IO object which has an encoding different from its external encoding, you can set its internal encoding. Ruby will use this internal encoding to transcode the data when it is read from the IO object.

Conversely, when data is written to the IO object it is transcoded from the internal encoding to the external encoding of the IO object.

The internal encoding of an IO object can be set with IO#set_encoding or at IO object creation (see IO.new options).

The internal encoding is optional and when not set, the Ruby default internal encoding is used. If not explicitly set this default internal encoding is nil meaning that by default, no transcoding occurs.

The default internal encoding can be set with the interpreter option -E. Encoding.default_internal returns the current internal encoding.

$ ruby -e 'p Encoding.default_internal'
nil

$ ruby -E ISO-8859-1:UTF-8 -e "p [Encoding.default_external, \
  Encoding.default_internal]"
[#<Encoding:ISO-8859-1>, #<Encoding:UTF-8>]

The default internal encoding may also be set through Encoding.default_internal=, but you should not do this as strings created before and after the change will have inconsistent encodings. Instead use ruby -E to invoke ruby with the correct internal encoding.

IO encoding example

In the following example a UTF-8 encoded string “Ru00E9sumu00E9” is transcoded for output to ISO-8859-1 encoding, then read back in and transcoded to UTF-8:

string = "R\u00E9sum\u00E9"

open("transcoded.txt", "w:ISO-8859-1") do |io|
  io.write(string)
end

puts "raw text:"
p File.binread("transcoded.txt")
puts

open("transcoded.txt", "r:ISO-8859-1:UTF-8") do |io|
  puts "transcoded text:"
  p io.read
end

While writing the file, the internal encoding is not specified as it is only necessary for reading. While reading the file both the internal and external encoding must be specified to obtain the correct result.

$ ruby t.rb
raw text:
"R\xE9sum\xE9"

transcoded text:
"R\u00E9sum\u00E9"

Exception

Class Exception and its subclasses are used to communicate between Kernel#raise and rescue statements in begin ... end blocks.

An Exception object carries information about an exception:

Some built-in subclasses of Exception have additional methods: e.g., NameError#name.

Defaults

Two Ruby statements have default exception classes:

Global Variables

When an exception has been raised but not yet handled (in rescue, ensure, at_exit and END blocks), two global variables are set:

Custom Exceptions

To provide additional or alternate information, a program may create custom exception classes that derive from the built-in exception classes.

A good practice is for a library to create a single “generic” exception class (typically a subclass of StandardError or RuntimeError) and have its other exception classes derive from that class. This allows the user to rescue the generic exception, thus catching all exceptions the library may raise even if future versions of the library add new exception subclasses.

For example:

class MyLibrary
  class Error < ::StandardError
  end

  class WidgetError < Error
  end

  class FrobError < Error
  end

end

To handle both MyLibrary::WidgetError and MyLibrary::FrobError the library user can rescue MyLibrary::Error.

Built-In Exception Classes

The built-in subclasses of Exception are:

SignalException

Raised when a signal is received.

begin
  Process.kill('HUP',Process.pid)
  sleep # wait for receiver to handle signal sent by Process.kill
rescue SignalException => e
  puts "received Exception #{e}"
end

produces:

received Exception SIGHUP

StandardError

The most standard error types are subclasses of StandardError. A rescue clause without an explicit Exception class will rescue all StandardErrors (and only those).

def foo
  raise "Oups"
end
foo rescue "Hello"   #=> "Hello"

On the other hand:

require 'does/not/exist' rescue "Hi"

raises the exception:

LoadError: no such file to load -- does/not/exist

EncodingError

EncodingError is the base class for encoding errors.

Rational

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:

You can convert certain objects to Rationals with:

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)

Struct

Class Struct provides a convenient way to create a simple class that can store and fetch values.

This example creates a subclass of Struct, Struct::Customer; the first argument, a string, is the name of the subclass; the other arguments, symbols, determine the members of the new subclass.

Customer = Struct.new('Customer', :name, :address, :zip)
Customer.name       # => "Struct::Customer"
Customer.class      # => Class
Customer.superclass # => Struct

Corresponding to each member are two methods, a writer and a reader, that store and fetch values:

methods = Customer.instance_methods false
methods # => [:zip, :address=, :zip=, :address, :name, :name=]

An instance of the subclass may be created, and its members assigned values, via method ::new:

joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
joe # => #<struct Struct::Customer name="Joe Smith", address="123 Maple, Anytown NC", zip=12345>

The member values may be managed thus:

joe.name    # => "Joe Smith"
joe.name = 'Joseph Smith'
joe.name    # => "Joseph Smith"

And thus; note that member name may be expressed as either a string or a symbol:

joe[:name]  # => "Joseph Smith"
joe[:name] = 'Joseph Smith, Jr.'
joe['name'] # => "Joseph Smith, Jr."

See Struct::new.

What’s Here

First, what’s elsewhere. Class Struct:

Here, class Struct provides methods that are useful for:

Methods for Creating a Struct Subclass

::new

Returns a new subclass of Struct.

Methods for Querying

hash

Returns the integer hash code.

length, size

Returns the number of members.

Methods for Comparing

#==

Returns whether a given object is equal to self, using == to compare member values.

eql?

Returns whether a given object is equal to self, using eql? to compare member values.

Methods for Fetching

[]

Returns the value associated with a given member name.

to_a, values, deconstruct

Returns the member values in self as an array.

deconstruct_keys

Returns a hash of the name/value pairs for given member names.

dig

Returns the object in nested objects that is specified by a given member name and additional arguments.

members

Returns an array of the member names.

select, filter

Returns an array of member values from self, as selected by the given block.

values_at

Returns an array containing values for given member names.

Methods for Assigning

[]=

Assigns a given value to a given member name.

Methods for Iterating

each

Calls a given block with each member name.

each_pair

Calls a given block with each member name/value pair.

Methods for Converting

inspect, to_s

Returns a string representation of self.

to_h

Returns a hash of the member name/value pairs in self.

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