Returns the locale charmap name. It returns nil if no appropriate information.
Debian GNU/Linux LANG=C Encoding.locale_charmap #=> "ANSI_X3.4-1968" LANG=ja_JP.EUC-JP Encoding.locale_charmap #=> "EUC-JP" SunOS 5 LANG=C Encoding.locale_charmap #=> "646" LANG=ja Encoding.locale_charmap #=> "eucJP"
The result is highly platform dependent. So Encoding.find(Encoding.locale_charmap)
may cause an error. If you need some encoding object even for unknown locale, Encoding.find
(“locale”) can be used.
Iterates the given block for each element with an index, which starts from offset
. If no block is given, returns a new Enumerator
that includes the index, starting from offset
offset
the starting index to use
Returns the singleton class of obj. This method creates a new singleton class if obj does not have one.
If obj is nil
, true
, or false
, it returns NilClass
, TrueClass
, or FalseClass
, respectively. If obj is an Integer
, a Float
or a Symbol
, it raises a TypeError
.
Object.new.singleton_class #=> #<Class:#<Object:0xb7ce1e24>> String.singleton_class #=> #<Class:String> nil.singleton_class #=> NilClass
Returns an array of the names of singleton methods for obj. If the optional all parameter is true, the list will include methods in modules included in obj. Only public and protected singleton methods are returned.
module Other def three() end end class Single def Single.four() end end a = Single.new def a.one() end class << a include Other def two() end end Single.singleton_methods #=> [:four] a.singleton_methods(false) #=> [:two, :one] a.singleton_methods #=> [:two, :one, :three]
Returns an array of instance variable names for the receiver. Note that simply defining an accessor does not create the corresponding instance variable.
class Fred attr_accessor :a1 def initialize @iv = 3 end end Fred.new.instance_variables #=> [:@iv]
Returns true
if obj is an instance of the given class. See also Object#kind_of?
.
class A; end class B < A; end class C < B; end b = B.new b.instance_of? A #=> false b.instance_of? B #=> true b.instance_of? C #=> false
Returns true
if class is the class of obj, or if class is one of the superclasses of obj or modules included in obj.
module M; end class A include M end class B < A; end class C < B; end b = B.new b.is_a? A #=> true b.is_a? B #=> true b.is_a? C #=> false b.is_a? M #=> true b.kind_of? A #=> true b.kind_of? B #=> true b.kind_of? C #=> false b.kind_of? M #=> true
Similar to method, searches singleton method only.
class Demo def initialize(n) @iv = n end def hello() "Hello, @iv = #{@iv}" end end k = Demo.new(99) def k.hi "Hi, @iv = #{@iv}" end m = k.singleton_method(:hi) m.call #=> "Hi, @iv = 99" m = k.singleton_method(:hello) #=> NameError
Returns an array of all modules used in the current scope. The ordering of modules in the resulting array is not defined.
module A refine Object do end end module B refine Object do end end using A using B p Module.used_refinements
produces:
[#<refinement:Object@B>, #<refinement:Object@A>]
Invoked as a callback whenever an instance method is undefined from the receiver.
module Chatty def self.method_undefined(method_name) puts "Undefining #{method_name.inspect}" end def self.some_class_method() end def some_instance_method() end class << self undef_method :some_class_method end undef_method :some_instance_method end
produces:
Undefining :some_instance_method
Returns the list of modules included or prepended in mod or one of mod’s ancestors.
module Sub end module Mixin prepend Sub end module Outer include Mixin end Mixin.included_modules #=> [Sub] Outer.included_modules #=> [Sub, Mixin]
Returns an array containing the names of the public and protected instance methods in the receiver. For a module, these are the public and protected methods; for a class, they are the instance (not singleton) methods. If the optional parameter is false
, the methods of any ancestors are not included.
module A def method1() end end class B include A def method2() end end class C < B def method3() end end A.instance_methods(false) #=> [:method1] B.instance_methods(false) #=> [:method2] B.instance_methods(true).include?(:method1) #=> true C.instance_methods(false) #=> [:method3] C.instance_methods.include?(:method2) #=> true
Note that method visibility changes in the current class, as well as aliases, are considered as methods of the current class by this method:
class C < B alias method4 method2 protected :method2 end C.instance_methods(false).sort #=> [:method2, :method3, :method4]
Says whether mod or its ancestors have a constant with the given name:
Float.const_defined?(:EPSILON) #=> true, found in Float itself Float.const_defined?("String") #=> true, found in Object (ancestor) BasicObject.const_defined?(:Hash) #=> false
If mod is a Module
, additionally Object
and its ancestors are checked:
Math.const_defined?(:String) #=> true, found in Object
In each of the checked classes or modules, if the constant is not present but there is an autoload for it, true
is returned directly without autoloading:
module Admin autoload :User, 'admin/user' end Admin.const_defined?(:User) #=> true
If the constant is not found the callback const_missing
is not called and the method returns false
.
If inherit
is false, the lookup only checks the constants in the receiver:
IO.const_defined?(:SYNC) #=> true, found in File::Constants (ancestor) IO.const_defined?(:SYNC, false) #=> false, not found in IO itself
In this case, the same logic for autoloading applies.
If the argument is not a valid constant name a NameError
is raised with the message “wrong constant name name”:
Hash.const_defined? 'foobar' #=> NameError: wrong constant name foobar
Returns true
if mod is a singleton class or false
if it is an ordinary class or module.
class C end C.singleton_class? #=> false C.singleton_class.singleton_class? #=> true
Returns an UnboundMethod
representing the given instance method in mod.
class Interpreter def do_a() print "there, "; end def do_d() print "Hello "; end def do_e() print "!\n"; end def do_v() print "Dave"; end Dispatcher = { "a" => instance_method(:do_a), "d" => instance_method(:do_d), "e" => instance_method(:do_e), "v" => instance_method(:do_v) } def interpret(string) string.each_char {|b| Dispatcher[b].bind(self).call } end end interpreter = Interpreter.new interpreter.interpret('dave')
produces:
Hello there, Dave!
Defines an instance method in the receiver. The method parameter can be a Proc
, a Method
or an UnboundMethod
object. If a block is specified, it is used as the method body. If a block or the method parameter has parameters, they’re used as method parameters. This block is evaluated using instance_eval
.
class A def fred puts "In Fred" end def create_method(name, &block) self.class.define_method(name, &block) end define_method(:wilma) { puts "Charge it!" } define_method(:flint) {|name| puts "I'm #{name}!"} end class B < A define_method(:barney, instance_method(:fred)) end a = B.new a.barney a.wilma a.flint('Dino') a.create_method(:betty) { p self } a.betty
produces:
In Fred Charge it! I'm Dino! #<B:0x401b39e8>
Returns true
if the named method is defined by mod. If inherit is set, the lookup will also search mod’s ancestors. Public and protected methods are matched. String
arguments are converted to symbols.
module A def method1() end def protected_method1() end protected :protected_method1 end class B def method2() end def private_method2() end private :private_method2 end class C < B include A def method3() end end A.method_defined? :method1 #=> true C.method_defined? "method1" #=> true C.method_defined? "method2" #=> true C.method_defined? "method2", true #=> true C.method_defined? "method2", false #=> false C.method_defined? "method3" #=> true C.method_defined? "protected_method1" #=> true C.method_defined? "method4" #=> false C.method_defined? "private_method2" #=> false
Execute the provided block, but preserve the precision limit
BigDecimal.limit(100) puts BigDecimal.limit BigDecimal.save_limit do BigDecimal.limit(200) puts BigDecimal.limit end puts BigDecimal.limit
Returns the value as an Integer
.
If the BigDecimal
is infinity or NaN, raises FloatDomainError
.
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 block with each remaining line read from the stream; returns self
. Does nothing if already at end-of-stream; See Line IO.
With no arguments given, reads lines as determined by line separator $/
:
f = File.new('t.txt') f.each_line {|line| p line } f.each_line {|line| fail 'Cannot happen' } f.close
Output:
"First line\n" "Second line\n" "\n" "Fourth line\n" "Fifth line\n"
With only string argument sep
given, reads lines as determined by line separator sep
; see Line Separator:
f = File.new('t.txt') f.each_line('li') {|line| p line } f.close
Output:
"First li" "ne\nSecond li" "ne\n\nFourth li" "ne\nFifth li" "ne\n"
The two special values for sep
are honored:
f = File.new('t.txt') # Get all into one string. f.each_line(nil) {|line| p line } f.close
Output:
"First line\nSecond line\n\nFourth line\nFifth line\n" f.rewind # Get paragraphs (up to two line separators). f.each_line('') {|line| p line }
Output:
"First line\nSecond line\n\n" "Fourth line\nFifth line\n"
With only integer argument limit
given, limits the number of bytes in each line; see Line Limit:
f = File.new('t.txt') f.each_line(8) {|line| p line } f.close
Output:
"First li" "ne\n" "Second l" "ine\n" "\n" "Fourth l" "ine\n" "Fifth li" "ne\n"
With arguments sep
and limit
given, combines the two behaviors:
Calls with the next line as determined by line separator sep
.
But returns no more bytes than are allowed by the limit.
Optional keyword argument chomp
specifies whether line separators are to be omitted:
f = File.new('t.txt') f.each_line(chomp: true) {|line| p line } f.close
Output:
"First line" "Second line" "" "Fourth line" "Fifth line"
Returns an Enumerator
if no block is given.
IO#each
is an alias for IO#each_line
.
Calls the given block with each codepoint in the stream; returns self
:
f = File.new('t.rus') a = [] f.each_codepoint {|c| a << c } a # => [1090, 1077, 1089, 1090] f.close
Returns an Enumerator
if no block is given.
Related: IO#each_byte
, IO#each_char
.
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.