When RubyGems is required, Kernel#require
is replaced with our own which is capable of loading gems on demand.
When you call require 'x'
, this is what happens:
If the file can be loaded from the existing Ruby
loadpath, it is.
Otherwise, installed gems are searched for a file that matches. If it’s found in gem ‘y’, that gem is activated (added to the loadpath).
The normal require
functionality of returning false if that file has already been loaded is preserved.
Returns a Binding
object, describing the variable and method bindings at the point of call. This object can be used when calling Binding#eval
to execute the evaluated command in this environment, or extracting its local variables.
class User def initialize(name, position) @name = name @position = position end def get_binding binding end end user = User.new('Joan', 'manager') template = '{name: @name, position: @position}' # evaluate template in context of the object eval(template, user.get_binding) #=> {:name=>"Joan", :position=>"manager"}
Binding#local_variable_get
can be used to access the variables whose names are reserved Ruby
keywords:
# This is valid parameter declaration, but `if` parameter can't # be accessed by name, because it is a reserved word. def validate(field, validation, if: nil) condition = binding.local_variable_get('if') return unless condition # ...Some implementation ... end validate(:name, :empty?, if: false) # skips validation validate(:name, :empty?, if: true) # performs validation
Returns the first element or elements.
With no argument, returns the first element, or nil
if there is none:
(1..4).first # => 1 %w[a b c].first # => "a" {foo: 1, bar: 1, baz: 2}.first # => [:foo, 1] [].first # => nil
With integer argument n
, returns an array containing the first n
elements that exist:
(1..4).first(2) # => [1, 2] %w[a b c d].first(3) # => ["a", "b", "c"] %w[a b c d].first(50) # => ["a", "b", "c", "d"] {foo: 1, bar: 1, baz: 2}.first(2) # => [[:foo, 1], [:bar, 1]] [].first(2) # => []
Returns a Digest
subclass by name
require 'openssl' OpenSSL::Digest("MD5") # => OpenSSL::Digest::MD5 Digest("Foo") # => NameError: wrong constant name Foo
Returns a Digest
subclass by name
require 'openssl' OpenSSL::Digest("MD5") # => OpenSSL::Digest::MD5 Digest("Foo") # => NameError: wrong constant name Foo
Disables garbage collection, returning true
if garbage collection was already disabled.
GC.disable #=> false GC.disable #=> true
Returns time stamp of the target
file if it exists and is newer than or equal to all of times
.
Returns a string usable in Dir.glob
to match all requirable paths for this spec.
Creates a new directory in the tar file name
with mode
Calls the given block once for each key
, value
pair in the database.
Returns self
.
Iterates over keys and values. Note that unlike other collections, each
without block isn’t supported.
@api private
Calls the given block with each successive character from self
; returns self
:
'hello'.each_char {|char| print char, ' ' } print "\n" 'тест'.each_char {|char| print char, ' ' } print "\n" 'こんにちは'.each_char {|char| print char, ' ' } print "\n"
Output:
h e l l o т е с т こ ん に ち は
Returns an enumerator if no block is given.
Changes the encoding of self
to encoding
, which may be a string encoding name or an Encoding
object; returns self:
s = 'łał' s.bytes # => [197, 130, 97, 197, 130] s.encoding # => #<Encoding:UTF-8> s.force_encoding('ascii') # => "\xC5\x82a\xC5\x82" s.encoding # => #<Encoding:US-ASCII>
Does not change the underlying bytes:
s.bytes # => [197, 130, 97, 197, 130]
Makes the change even if the given encoding
is invalid for self
(as is the change above):
s.valid_encoding? # => false s.force_encoding(Encoding::UTF_8) # => "łał" s.valid_encoding? # => true
Returns true
if self
is encoded correctly, false
otherwise:
"\xc2\xa1".force_encoding(Encoding::UTF_8).valid_encoding? # => true "\xc2".force_encoding(Encoding::UTF_8).valid_encoding? # => false "\x80".force_encoding(Encoding::UTF_8).valid_encoding? # => false
Returns true
if the arguments define a valid ordinal date, false
otherwise:
Date.valid_ordinal?(2001, 34) # => true Date.valid_ordinal?(2001, 366) # => false
See argument start.
Related: Date.jd
, Date.ordinal
.
Calls the given block with each character in the stream; returns self
. See Character IO.
f = File.new('t.rus') a = [] f.each_char {|c| a << c.ord } a # => [1090, 1077, 1089, 1090] f.close
Returns an Enumerator
if no block is given.
Related: IO#each_byte
, IO#each_codepoint
.
Returns the Encoding
object that represents the encoding of the stream, or nil
if the stream is in write mode and no encoding is specified.
See Encodings.
Returns the Encoding
object that represents the encoding of the internal string, if conversion is specified, or nil
otherwise.
See Encodings.
See Encodings.
Argument ext_enc
, if given, must be an Encoding
object or a String
with the encoding name; it is assigned as the encoding for the stream.
Argument int_enc
, if given, must be an Encoding
object or a String
with the encoding name; it is assigned as the encoding for the internal string.
Argument 'ext_enc:int_enc'
, if given, is a string containing two colon-separated encoding names; corresponding Encoding
objects are assigned as the external and internal encodings for the stream.
If the external encoding of a string is binary/ASCII-8BIT, the internal encoding of the string is set to nil, since no transcoding is needed.
Optional keyword arguments enc_opts
specify Encoding options.
Returns false
if self
is applicable to a string with any ASCII-compatible encoding; otherwise returns true
:
r = /a/ # => /a/ r.fixed_encoding? # => false r.match?("\u{6666} a") # => true r.match?("\xa1\xa2 a".force_encoding("euc-jp")) # => true r.match?("abc".force_encoding("euc-jp")) # => true r = /a/u # => /a/ r.fixed_encoding? # => true r.match?("\u{6666} a") # => true r.match?("\xa1\xa2".force_encoding("euc-jp")) # Raises exception. r.match?("abc".force_encoding("euc-jp")) # => true r = /\u{6666}/ # => /\u{6666}/ r.fixed_encoding? # => true r.encoding # => #<Encoding:UTF-8> r.match?("\u{6666} a") # => true r.match?("\xa1\xa2".force_encoding("euc-jp")) # Raises exception. r.match?("abc".force_encoding("euc-jp")) # => false
Iterates over the children of the directory (files and subdirectories, not recursive).
It yields Pathname
object for each child.
By default, the yielded pathnames will have enough information to access the files.
If you set with_directory
to false
, then the returned pathnames will contain the filename only.
Pathname("/usr/local").each_child {|f| p f } #=> #<Pathname:/usr/local/share> # #<Pathname:/usr/local/bin> # #<Pathname:/usr/local/games> # #<Pathname:/usr/local/lib> # #<Pathname:/usr/local/include> # #<Pathname:/usr/local/sbin> # #<Pathname:/usr/local/src> # #<Pathname:/usr/local/man> Pathname("/usr/local").each_child(false) {|f| p f } #=> #<Pathname:share> # #<Pathname:bin> # #<Pathname:games> # #<Pathname:lib> # #<Pathname:include> # #<Pathname:sbin> # #<Pathname:src> # #<Pathname:man>
Note that the results never contain the entries .
and ..
in the directory because they are not children.
With a block given, calls the block with each remaining character in the stream; see Character IO.
With no block given, returns an enumerator.
Returns the Encoding
object that represents the encoding of the file. If the stream is write mode and no encoding is specified, returns nil
.