Results for: "String#[]"

Returns the index of a specified element.

When argument object is given but no block, returns the index of the first element element for which object == element:

a = [:foo, 'bar', 2, 'bar']
a.index('bar') # => 1

Returns nil if no such element found.

When both argument object and a block are given, calls the block with each successive element; returns the index of the first element for which the block returns a truthy value:

a = [:foo, 'bar', 2, 'bar']
a.index {|element| element == 'bar' } # => 1

Returns nil if the block never returns a truthy value.

When neither an argument nor a block is given, returns a new Enumerator:

a = [:foo, 'bar', 2]
e = a.index
e # => #<Enumerator: [:foo, "bar", 2]:index>
e.each {|element| element == 'bar' } # => 1

Array#find_index is an alias for Array#index.

Related: rindex.

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 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

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

Creates an accessor method to allow assignment to the attribute symbol.id2name. String arguments are converted to symbols. Returns an array of defined method names as symbols.

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

Makes a list of existing constants private.

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!

Returns a hash of the name/value pairs, to use in pattern matching. Possible keys are: :year, :month, :day, :wday, :yday.

Possible usages:

d = Date.new(2022, 10, 5)

if d in wday: 3, day: ..7  # uses deconstruct_keys underneath
  puts "first Wednesday of the month"
end
#=> prints "first Wednesday of the month"

case d
in year: ...2022
  puts "too old"
in month: ..9
  puts "quarter 1-3"
in wday: 1..5, month:
  puts "working day in month #{month}"
end
#=> prints "working day in month 10"

Note that deconstruction by pattern can also be combined with class check:

if d in Date(wday: 3, day: ..7)
  puts "first Wednesday of the month"
end

Returns a hash of the name/value pairs, to use in pattern matching. Possible keys are: :year, :month, :day, :wday, :yday, :hour, :min, :sec, :sec_fraction, :zone.

Possible usages:

dt = DateTime.new(2022, 10, 5, 13, 30)

if d in wday: 1..5, hour: 10..18  # uses deconstruct_keys underneath
  puts "Working time"
end
#=> prints "Working time"

case dt
in year: ...2022
  puts "too old"
in month: ..9
  puts "quarter 1-3"
in wday: 1..5, month:
  puts "working day in month #{month}"
end
#=> prints "working day in month 10"

Note that deconstruction by pattern can also be combined with class check:

if d in DateTime(wday: 1..5, hour: 10..18, day: ..7)
  puts "Working time, first week of the month"
end

Returns a hash of the name/value pairs, to use in pattern matching. Possible keys are: :year, :month, :day, :yday, :wday, :hour, :min, :sec, :subsec, :dst, :zone.

Possible usages:

t = Time.utc(2022, 10, 5, 21, 25, 30)

if t in wday: 3, day: ..7  # uses deconstruct_keys underneath
  puts "first Wednesday of the month"
end
#=> prints "first Wednesday of the month"

case t
in year: ...2022
  puts "too old"
in month: ..9
  puts "quarter 1-3"
in wday: 1..5, month:
  puts "working day in month #{month}"
end
#=> prints "working day in month 10"

Note that deconstruction by pattern can also be combined with class check:

if t in Time(wday: 3, day: ..7)
  puts "first Wednesday of the month"
end

Waits until IO is priority and returns a truthy value or a falsy value when times out. Priority data is sent and received using the Socket::MSG_OOB flag and is typically limited to streams.

You must require ‘io/wait’ to use this method.

Copies from the given src to the given dst, returning the number of bytes copied.

• The given src must be one of the following:

  • The path to a readable file, from which source data is to be read.

  • An IO-like object, opened for reading and capable of responding to method :readpartial or method :read.

• The given dst must be one of the following:

  • The path to a writable file, to which data is to be written.

  • An IO-like object, opened for writing and capable of responding to method :write.

The examples here use file t.txt as source:

File.read('t.txt')
# => "First line\nSecond line\n\nThird line\nFourth line\n"
File.read('t.txt').size # => 47

If only arguments src and dst are given, the entire source stream is copied:

# Paths.
IO.copy_stream('t.txt', 't.tmp')  # => 47

# IOs (recall that a File is also an IO).
src_io = File.open('t.txt', 'r') # => #<File:t.txt>
dst_io = File.open('t.tmp', 'w') # => #<File:t.tmp>
IO.copy_stream(src_io, dst_io)   # => 47
src_io.close
dst_io.close

With argument src_length a non-negative integer, no more than that many bytes are copied:

IO.copy_stream('t.txt', 't.tmp', 10) # => 10
File.read('t.tmp')                   # => "First line"

With argument src_offset also given, the source stream is read beginning at that offset:

IO.copy_stream('t.txt', 't.tmp', 11, 11) # => 11
IO.read('t.tmp')                         # => "Second line"

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.

See Encodings.

Argument ext_enc, if given, must be an Encoding object; it is assigned as the encoding for the stream.

Argument int_enc, if given, must be an Encoding object; 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.

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

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

Customer = Struct.new(:name, :address, :zip)
joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
h = joe.deconstruct_keys([:zip, :address])
h # => {:zip=>12345, :address=>"123 Maple, Anytown NC"}

Returns all names and values if array_of_names is nil:

h = joe.deconstruct_keys(nil)
h # => {:name=>"Joseph Smith, Jr.", :address=>"123 Maple, Anytown NC", :zip=>12345}

creates an Addrinfo object from the arguments.

The arguments are interpreted as similar to self.

Addrinfo.tcp("0.0.0.0", 4649).family_addrinfo("www.ruby-lang.org", 80)
#=> #<Addrinfo: 221.186.184.68:80 TCP (www.ruby-lang.org:80)>

Addrinfo.unix("/tmp/sock").family_addrinfo("/tmp/sock2")
#=> #<Addrinfo: /tmp/sock2 SOCK_STREAM>

Returns the Encoding object that represents the encoding of the file. If the stream is write mode and no encoding is specified, returns nil.

Specify the encoding of the StringIO as ext_enc. Use the default external encoding if ext_enc is nil. 2nd argument int_enc and optional hash opt argument are ignored; they are for API compatibility to IO.

Calls WIN32OLE#invoke method.

Evaluates a string containing Ruby source code, or the given block, within the context of the receiver (obj). In order to set the context, the variable self is set to obj while the code is executing, giving the code access to obj’s instance variables and private methods.

When instance_eval is given a block, obj is also passed in as the block’s only argument.

When instance_eval is given a String, the optional second and third parameters supply a filename and starting line number that are used when reporting compilation errors.

class KlassWithSecret
  def initialize
    @secret = 99
  end
  private
  def the_secret
    "Ssssh! The secret is #{@secret}."
  end
end
k = KlassWithSecret.new
k.instance_eval { @secret }          #=> 99
k.instance_eval { the_secret }       #=> "Ssssh! The secret is 99."
k.instance_eval {|obj| obj == self } #=> true