Class: Proc

Inherits:
Object show all
Defined in:
eval.c

Overview

Proc objects are blocks of code that have been bound to a set of local variables. Once bound, the code may be called in different contexts and still access those variables.

def gen_times(factor)
  return Proc.new {|n| n*factor }
end

times3 = gen_times(3)
times5 = gen_times(5)

times3.call(12)               #=> 36
times5.call(5)                #=> 25
times3.call(times5.call(4))   #=> 60

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.new {|...| ... } ⇒ Proc .new ⇒ Proc

Creates a new Proc object, bound to the current context. Proc::new may be called without a block only within a method with an attached block, in which case that block is converted to the Proc object.

def proc_from
  Proc.new
end
proc = proc_from { "hello" }
proc.call   #=> "hello"

Overloads:

  • .new {|...| ... } ⇒ Proc

    Yields:

    • (...)

    Returns:

  • .new ⇒ Proc

    Returns:



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# File 'eval.c', line 8726

static VALUE
proc_s_new(argc, argv, klass)
int argc;

Instance Method Details

#==(other_proc) ⇒ Boolean

Return true if prc is the same object as other_proc, or if they are both procs with the same body.

Returns:

  • (Boolean) 


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# File 'eval.c', line 8982

static VALUE
proc_eq(self, other)
VALUE self, other;

#call(params, ...) ⇒ Object #[](params, ...) ⇒ Object

Invokes the block, setting the block’s parameters to the values in params using something close to method calling semantics. Generates a warning if multiple values are passed to a proc that expects just one (previously this silently converted the parameters to an array).

For procs created using Kernel.proc, generates an error if the wrong number of parameters are passed to a proc with multiple parameters. For procs created using Proc.new, extra parameters are silently discarded.

Returns the value of the last expression evaluated in the block. See also Proc#yield.

a_proc = Proc.new {|a, *b| b.collect {|i| i*a }}
a_proc.call(9, 1, 2, 3)   #=> [9, 18, 27]
a_proc[9, 1, 2, 3]        #=> [9, 18, 27]
a_proc = Proc.new {|a,b| a}
a_proc.call(1,2,3)

produces:

prog.rb:5: wrong number of arguments (3 for 2) (ArgumentError)
  from prog.rb:4:in `call'
  from prog.rb:5

Overloads:



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# File 'eval.c', line 8905

VALUE
rb_proc_call(proc, args)
VALUE proc, args;

#arity ⇒ Fixnum

Returns the number of arguments that would not be ignored. If the block is declared to take no arguments, returns 0. If the block is known to take exactly n arguments, returns n. If the block has optional arguments, return -n-1, where n is the number of mandatory arguments. A proc with no argument declarations is the same a block declaring || as its arguments.

Proc.new {}.arity          #=>  0
Proc.new {||}.arity        #=>  0
Proc.new {|a|}.arity       #=>  1
Proc.new {|a,b|}.arity     #=>  2
Proc.new {|a,b,c|}.arity   #=>  3
Proc.new {|*a|}.arity      #=> -1
Proc.new {|a,*b|}.arity    #=> -2

Returns:



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# File 'eval.c', line 8935

static VALUE
proc_arity(proc)
VALUE proc;

#binding ⇒ Binding

Returns the binding associated with prc. Note that Kernel#eval accepts either a Proc or a Binding object as its second parameter.

def fred(param)
  proc {}
end

b = fred(99)
eval("param", b.binding)   #=> 99
eval("param", b)           #=> 99

Returns:



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# File 'eval.c', line 9074

static VALUE
proc_binding(proc)
VALUE proc;

#call(params, ...) ⇒ Object #[](params, ...) ⇒ Object

Invokes the block, setting the block’s parameters to the values in params using something close to method calling semantics. Generates a warning if multiple values are passed to a proc that expects just one (previously this silently converted the parameters to an array).

For procs created using Kernel.proc, generates an error if the wrong number of parameters are passed to a proc with multiple parameters. For procs created using Proc.new, extra parameters are silently discarded.

Returns the value of the last expression evaluated in the block. See also Proc#yield.

a_proc = Proc.new {|a, *b| b.collect {|i| i*a }}
a_proc.call(9, 1, 2, 3)   #=> [9, 18, 27]
a_proc[9, 1, 2, 3]        #=> [9, 18, 27]
a_proc = Proc.new {|a,b| a}
a_proc.call(1,2,3)

produces:

prog.rb:5: wrong number of arguments (3 for 2) (ArgumentError)
  from prog.rb:4:in `call'
  from prog.rb:5

Overloads:



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# File 'eval.c', line 8905

VALUE
rb_proc_call(proc, args)
VALUE proc, args;

#clone ⇒ Object

MISSING: documentation



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# File 'eval.c', line 8491

static VALUE
proc_clone(self)
VALUE self;

#dup ⇒ Object 



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# File 'eval.c', line 8516

static VALUE
proc_dup(self)
VALUE self;

#to_proc ⇒ Proc

Part of the protocol for converting objects to Proc objects. Instances of class Proc simply return themselves.

Returns:



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# File 'eval.c', line 9050

static VALUE
proc_to_self(self)
VALUE self;

#to_s ⇒ String

Shows the unique identifier for this proc, along with an indication of where the proc was defined.

Returns:



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# File 'eval.c', line 9011

static VALUE
proc_to_s(self)
VALUE self;