Method call within a class

Hi all,

Maybe I miss something. But I am confused about method call within a
class. What is the format for that? I just copy some code segments from
the forum as follows:

module Enumerable
def each_with_index
i = 0
each do |elem|
yield elem, i
i += 1
end
end
end

class Array
def each_with_index
size.times do |i|
yield self[i], i
end
end
end

So

  1. which one is the reciever for “each”?
  2. which one is the reciever for “size”?

Do they default to self?

Thanks,

Li

Hei,

“each”'s receiver will be an instance of a class that includes the
module Enumerable and “size”'s receiver will be an instance of the class
Array. Example:

array = Array.new
p array.size # => 0

class MyEnumerable
include Enumerable

end

foo = MyEnumerable.new
foo.each_with_index # doesn’t raise, the method is defined

HTH


Andrea D.
http://github.com/bolthar/freightrain
http://usingimho.wordpress.com

Andrea D. wrote:

Hei,

“each”'s receiver will be an instance of a class that includes the
module Enumerable and “size”'s receiver will be an instance of the class
Array. Example:

array = Array.new
p array.size # => 0

class MyEnumerable
include Enumerable

end

foo = MyEnumerable.new
foo.each_with_index # doesn’t raise, the method is defined

Hi Andrea,

Thank you very much. So the receiver can be omitted when the method is
called within a class, right?

Li

Hei Li,

yes, the default deceiver is ‘self’ so, if omitted, the receiver for
any message will be the istance itself.


Andrea D.
http://github.com/bolthar/freightrain
http://usingimho.wordpress.com

On Sun, Apr 11, 2010 at 2:15 PM, Li Chen removed_email_addre[email protected] wrote:

Hi Andrea,

Thank you very much. So the receiver can be omitted when the method is
called within a class, right?

Li

Posted via http://www.ruby-forum.com/.

Except on assignments, because it looks like you are creating a local
variable.
Example:

class Foo
attr_accessor :bar
def bad_assign
bar = ‘baz’
defined? bar
end
def good_assign
self.bar = ‘baz’
defined? bar
end
end

foo = Foo.new

foo.bad_assign # => “local-variable”
foo.bar # => nil

foo.good_assign # => “method”
foo.bar # => “baz”

Josh C. wrote:

On Sun, Apr 11, 2010 at 2:15 PM, Li Chen [email protected] wrote:

Hi Andrea,
Except on assignments, because it looks like you are creating a local
variable.
Example:

class Foo
attr_accessor :bar
def bad_assign
bar = ‘baz’
defined? bar
end
def good_assign
self.bar = ‘baz’
defined? bar
end
end

foo = Foo.new

foo.bad_assign # => “local-variable”
foo.bar # => nil

foo.good_assign # => “method”
foo.bar # => “baz”

Thank you so much. Where can I find more info about this usage?

Li

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