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:



8472
8473
8474
 
# File 'eval.c', line 8472

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) 


8720
8721
8722
 
# File 'eval.c', line 8720

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:



8649
8650
8651
 
# File 'eval.c', line 8649

static VALUE
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:



8679
8680
8681
 
# File 'eval.c', line 8679

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:



8812
8813
8814
 
# File 'eval.c', line 8812

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:



8649
8650
8651
 
# File 'eval.c', line 8649

static VALUE
proc_call(proc, args)
VALUE proc, args;

#clone ⇒ Object

MISSING: documentation



8284
8285
8286
 
# File 'eval.c', line 8284

static VALUE
proc_clone(self)
VALUE self;

#dup ⇒ Object

MISSING: documentation



8303
8304
8305
 
# File 'eval.c', line 8303

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:



8788
8789
8790
 
# File 'eval.c', line 8788

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:



8749
8750
8751
 
# File 'eval.c', line 8749

static VALUE
proc_to_s(self)
VALUE self;