- Inheritance
- < Object
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
Methods
Class
| Visibility | Signature |
|---|---|
| public | new (...) |
Instance
| Visibility | Signature |
|---|---|
| public | == (p1) |
| public | [] (...) |
| public | arity () |
| public | binding () |
| public | call (...) |
| public | clone () |
| public | to_proc () |
| public | to_s () |
Class Method Detail
Proc.new {|...| block } => a_proc
Proc.new => a_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"
Instance Method Detail
prc == other_proc => true or false
Return true if prc is the same object as other_proc, or if they are both procs with the same body.
prc.call(params,...) => obj
prc[params,...] => obj
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
prc.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
prc.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
prc.call(params,...) => obj
prc[params,...] => obj
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
clone()
MISSING: documentation
prc.to_proc → prc
Part of the protocol for converting objects to Proc objects. Instances of class Proc simply return themselves.
prc.to_s => string
Shows the unique identifier for this proc, along with an indication of where the proc was defined.