What's different between self.method and class << self?

ruby-talk
1

we can define a instance method in lots way.
mostly, I saw people define like this:
1.
class A
  def self.class_method
  #some code here....
  end
end

2.
class A
  class << self
    def class_method
    #some code here....
    end
  end
end

···

==
the question confused me is what's the advantage of doing this in 2?
they'are different? which is your choose?
--
Posted via http://www.ruby-forum.com/.

2

I asked this same question just a couple of weeks ago. The answers I was
given were:

Method 2:
1) Saves some typing
2) Has a slightly different mechanism for looking up class constants, which
99.99% of the time won't be noticed.

Other than that there are no differences between methods 1 & 2.

--wpd

···

On Tue, Oct 21, 2008 at 3:23 AM, Zhenning Guan <g.zhen.ning@gmail.com>wrote:

we can define a instance method in lots way.
mostly, I saw people define like this:
1.
class A
def self.class_method
#some code here....
end
end

2.
class A
class << self
   def class_method
   #some code here....
   end
end
end

==
the question confused me is what's the advantage of doing this in 2?
they'are different? which is your choose?

3

Zhenning Guan:

we can define a instance method in lots way.
mostly, I saw people define like this:
1.
class A
  def self.class_method
  #some code here....
  end
end

2.
class A
  class << self
    def class_method
    #some code here....
    end
  end
end

the question confused me is what's the advantage of doing this in 2?

You can work on the singleton’s properties with attr_* methods:

class Example
  class << self
    attr_accessor :prop
  end
end

(With the first approach you’d have to define self.prop and
self.prop= to be able to write code like Example.prop = 'value'.)

-- Shot

···

--
Damn, I need to rant, not whimper. Someone bring me a user. -- Wayne Pascoe

4

Patrick Doyle wrote:

···

On Tue, Oct 21, 2008 at 3:23 AM, Zhenning Guan > <g.zhen.ning@gmail.com>wrote:

class A
they'are different? which is your choose?

I asked this same question just a couple of weeks ago. The answers I
was
given were:

Method 2:
1) Saves some typing
2) Has a slightly different mechanism for looking up class constants,
which
99.99% of the time won't be noticed.

Other than that there are no differences between methods 1 & 2.

--wpd

what's the meaning of saves some typing???
can you give me a example?
--
Posted via http://www.ruby-forum.com/\.

5

Shot (Piotr Szotkowski):

(With the first approach you’d have to define self.prop and
self.prop= to be able to write code like Example.prop = 'value'.)

…or use something like Rails’ cattr_* accessors – but they work on
class variables (as opposed to instance variables of the singleton.)

-- Shot

···

--
Life being what it is, one dreams of revenge. -- Paul Gauguin

6

what's the meaning of saves some typing???
can you give me a example?
--
Posted via http://www.ruby-forum.com/\.

Instead of having to type

def self.method
   blah
   blah
   blah
end

you can type (within the class << self clause)

def method
  blah
  blah
  blah
end

I didn't say it would save you a _lot_ of typing, just some :slight_smile:

--wpd