Hiii,
i am new to this ruby-talk list, so i hope my question is not annoying
(especially for my not so goood english).
My question is simple. Is there a way to store a method in a variable? I
know that every method can be called with the keyword and send, but is
there a way to make it direct callable?
As example:
def addition(a, b)
a + b
end
x = addition
x(2, 3) # => 5
Is there a method like partial or anything like this in ruby?
best wishes,
Adrian
___
@addisaden
Hiii,
Hi!
i am new to this ruby-talk list, so i hope my question is not annoying
(especially for my not so goood english).
Not at all. As you might have seen from other messages today, we're
hungry for some actual Ruby discussion.
My question is simple. Is there a way to store a method in a variable? I
know that every method can be called with the keyword and send, but is
there a way to make it direct callable?
Yes. Functions and methods (they're both the same construct really) can
be held in objects of the Method class, which are obtained by calling
`obj.method(:method_name)`. Omit the receiver for functions/global
methods like `puts`.
As example:
def addition(a, b)
a + b
endx = addition
x(2, 3) # => 5Is there a method like partial or anything like this in ruby?
See this snippet:
def addition(a, b)
a + b
end
x = method(:addition)
puts x.call(2, 3)
puts x[2, 3] # syntax sugar; however, note instead of ()
class Foo
attr_accessor :a
def initialize(a)
self.a = a
end
def addition(b)
self.a + b
end
end
# For methods inside of classes:
f = Foo.new(2)
x = f.method(:addition)
puts x.call(3)
puts x[3]
On Mon, Jun 30, 2014, Addis Aden wrote:
best wishes,
Adrian
___
@addisaden
2.0.0p195 :001 > def addition(a, b)
2.0.0p195 :002?> a + b
2.0.0p195 :003?> end
2.0.0p195 :006 > x = method(:addition)
=> #<Method: Object#addition>
2.0.0p195 :010 > x.call 2, 3
=> 5
The standalone method is still bound to the object:
2.0.0p195 :011 > class A
2.0.0p195 :012?> def initialize a
2.0.0p195 :013?> @a = a
2.0.0p195 :014?> end
2.0.0p195 :015?> def addition y
2.0.0p195 :016?> @a + y
2.0.0p195 :017?> end
2.0.0p195 :018?> end
=> nil
2.0.0p195 :019 > a = A.new 3
=> #<A:0x000000026024b0 @a=3>
2.0.0p195 :022 > x = a.method :addition
=> #<Method: A#addition>
2.0.0p195 :023 > x.call 4
=> 7
You can also get an unbound method, but you can only call it after
binding it to an object of the same class (kind_of):
2.0.0p195 :026 > u = x.unbind
=> #<UnboundMethod: A#addition>
2.0.0p195 :027 > u.call 4
NoMethodError: undefined method `call' for #<UnboundMethod: A#addition>
2.0.0p195 :028 > b = u.bind(A.new 12)
=> #<Method: A#addition>
2.0.0p195 :029 > b.call 4
=> 16
Hope this helps,
Jesus.
On Mon, Jun 30, 2014 at 5:58 PM, Addis Aden <addis.aden@gmail.com> wrote:
Hiii,
i am new to this ruby-talk list, so i hope my question is not annoying
(especially for my not so goood english).My question is simple. Is there a way to store a method in a variable? I
know that every method can be called with the keyword and send, but is there
a way to make it direct callable?As example:
def addition(a, b)
a + b
endx = addition
x(2, 3) # => 5Is there a method like partial or anything like this in ruby?
Its that easy. Wow, thank you. never heard of the method method 
Seems that the Method than works like a Proc? I guess that the only
difference is, that a Proc isnt bound to an object ^^
2014-06-30 18:11 GMT+02:00 Eric Christopherson <echristopherson@gmail.com>:
On Mon, Jun 30, 2014, Addis Aden wrote:
> Hiii,Hi!
>
> i am new to this ruby-talk list, so i hope my question is not annoying
> (especially for my not so goood english).Not at all. As you might have seen from other messages today, we're
hungry for some actual Ruby discussion.>
> My question is simple. Is there a way to store a method in a variable? I
> know that every method can be called with the keyword and send, but is
> there a way to make it direct callable?Yes. Functions and methods (they're both the same construct really) can
be held in objects of the Method class, which are obtained by calling
`obj.method(:method_name)`. Omit the receiver for functions/global
methods like `puts`.>
> As example:
>
> def addition(a, b)
> a + b
> end
>
> x = addition
> x(2, 3) # => 5
>
> Is there a method like partial or anything like this in ruby?See this snippet:
def addition(a, b)
a + b
endx = method(:addition)
puts x.call(2, 3)
puts x[2, 3] # syntax sugar; however, note instead of ()class Foo
attr_accessor :adef initialize(a)
self.a = a
enddef addition(b)
self.a + b
end
end# For methods inside of classes:
f = Foo.new(2)
x = f.method(:addition)
puts x.call(3)
puts x[3]>
> best wishes,
>
> Adrian
>
> ___
> @addisaden
Its that easy. Wow, thank you. never heard of the method method
Seems that the Method than works like a Proc? I guess that the only
difference is, that a Proc isnt bound to an object ^^
A Proc is a closure which a method is not. A Method only catches self
i.e. the object which will receive the call. An UnboundMethod does
not even do that.
A closure captures variables from the surrounding scope
$ ruby -e 'x = 9; f = lambda {|y| x + y};p f.call(7)'
16
... which can even be changed:
$ ruby -e 'x = 9; f = lambda {|y| x + y};p f.call(7);x = 100; p f.call(7)'
16
107
Kind regards
robert
On Tue, Jul 1, 2014 at 10:50 AM, Addis Aden <addis.aden@gmail.com> wrote:
--
[guy, jim].each {|him| remember.him do |as, often| as.you_can - without end}
http://blog.rubybestpractices.com/
Ohh, scope matters Thank you for the hint ^^
This topic gives a new perspective for a lot ^^
2014-07-01 11:37 GMT+02:00 Robert Klemme <shortcutter@googlemail.com>:
On Tue, Jul 1, 2014 at 10:50 AM, Addis Aden <addis.aden@gmail.com> wrote:
> Its that easy. Wow, thank you. never heard of the method method
> Seems that the Method than works like a Proc? I guess that the only
> difference is, that a Proc isnt bound to an object ^^A Proc is a closure which a method is not. A Method only catches self
i.e. the object which will receive the call. An UnboundMethod does
not even do that.A closure captures variables from the surrounding scope
$ ruby -e 'x = 9; f = lambda {|y| x + y};p f.call(7)'
16... which can even be changed:
$ ruby -e 'x = 9; f = lambda {|y| x + y};p f.call(7);x = 100; p f.call(7)'
16
107Kind regards
robert
--
[guy, jim].each {|him| remember.him do |as, often| as.you_can - without
end}
http://blog.rubybestpractices.com/