Calling class method from instance

ruby-talk
1

I was puzzled on this but figured out a way to do it. Figured I'd post
it on here, maybe there's a better way ..

class Test

@c = 2
def self.ctest
   puts @c
end

def initialize(i)
  @i = i
end

def itest
  puts @i
# here's what I was trying to do !!!
  puts self.class.ctest
end

end

ob = Test.new(7)

ob.itest
Test.ctest

2

IMHO this call syntax is optimal, because agnostic to the class name.
Robert

···

On Tue, Feb 10, 2009 at 5:19 PM, Larz <wbsurfver@gmail.com> wrote:

puts self.class.ctest

--
It is change, continuing change, inevitable change, that is the
dominant factor in society today. No sensible decision can be made any
longer without taking into account not only the world as it is, but
the world as it will be ... ~ Isaac Asimov

3

Larz wrote:

  puts self.class.ctest

What's the reason for not simply writing your class like this:

class Test
  @c = 20

  def Test.a
    puts @c
  end

  def b
    Test.a
  end

end

t = Test.new
t.b

--output:--
20

···

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

4

Larz wrote:

def itest
  puts @i
# here's what I was trying to do !!!
  puts self.class.ctest
end

I think Object#class is something to be avoided in most cases. Frankly
it's none of your business what class was used to create an object. It
doesn't matter _how_ an object sprang into existence, what matters is
how it quacks.

I want to replace an object with a delegate with no ill effects. Or
with a mock object, or with whatever. But uses of Object#class defeat
this.

I would be inclined to make shared data explicit either with a constant
or a with a passed-in reference to the shared data, rather than implicit
with Object#class.

class Test
  SHARED = Struct.new(:ctest).new(2)

  def itest
    puts SHARED.ctest
  end
end

Test.new.itest #=> 2

···

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

5

That's fine unless you want to, say, override the class method in a subclass

class TestSub < Test

  def TestSub.a
      puts "doin my own thang."
  end
end

t = TestSub.new
t.b
--output is still--
20

···

On Tue, Feb 10, 2009 at 3:27 PM, 7stud -- <bbxx789_05ss@yahoo.com> wrote:

Larz wrote:

> puts self.class.ctest

What's the reason for not simply writing your class like this:

class Test
@c = 20

def Test.a
   puts @c
end

def b
   Test.a
end

end

t = Test.new
t.b

--output:--
20
--

--
Rick DeNatale

Blog: http://talklikeaduck.denhaven2.com/
Twitter: http://twitter.com/RickDeNatale

6

<snip>

That's fine unless you want to, say, override the class method in a subclass

Good point, but there is another issue here.
Your project guru comes along and tells you: Nice code, but we should
not use the name Test (for a dumb reason of course).
Now you have to change Test to Check in your source
would you prefer to change it here

class Test
   def a # multiply this with n entries
      self.class.x
   end
   def self.a
     ...

or here

class Test
   def a
      Test.x
   end
   def Test.a

end

In other words the second version is not DRY and the worst penalty for
unDRYness is the need to change your code.

Robert

···

On Tue, Feb 10, 2009 at 11:21 PM, Rick DeNatale <rick.denatale@gmail.com> wrote:

--
It is change, continuing change, inevitable change, that is the
dominant factor in society today. No sensible decision can be made any
longer without taking into account not only the world as it is, but
the world as it will be ... ~ Isaac Asimov