Dynamic changes!

ruby-talk
1

These are the sequence of actions I performed in irb.

  class Dumber
    def sayHello
      puts "Hello!"
    end
  end
  
  db = Dumber.new()

  db.sayHello
  ## executes sayHello method!

  Class Dumber
    def sayHi
      puts "Hi"
    end
  end

  db.sayHi
  ## executes the newly added method sayHi!

   how does the object already created aware of the newly added method?

···

--
_ _ _]{5pitph!r3}[_ _ _
__________________________________________________
“I'm smart enough to know that I'm dumb.”
   - Richard P Feynman

2

The method is added to it's *class* - and that relationship does not change, only the class changes.

$ irb
irb(main):001:0> class Dumber
irb(main):002:1> def say_hello() puts "hello" end
irb(main):003:1> end
=> nil
irb(main):004:0> Dumber.instance_methods.grep /^say_/
=> ["say_hello"]
irb(main):005:0> Dumber.object_id
=> 1913790
irb(main):006:0> class Dumber
irb(main):007:1> def say_hi() puts "hi" end
irb(main):008:1> end
=> nil
irb(main):009:0> Dumber.instance_methods.grep /^say_/
=> ["say_hi", "say_hello"]
irb(main):010:0> Dumber.object_id
=> 1913790

As you see, Dumber stays the same instance, there are no multiple versions of it.

Kind regards

  robert

···

On 25.12.2006 19:37, Spitfire wrote:

These are the sequence of actions I performed in irb.

    class Dumber
        def sayHello
            puts "Hello!"
        end
    end
        db = Dumber.new()

    db.sayHello
    ## executes sayHello method!

    Class Dumber
        def sayHi
            puts "Hi"
        end
    end

    db.sayHi
    ## executes the newly added method sayHi!

  how does the object already created aware of the newly added method?

3

Robert Klemme wrote:

···

On 25.12.2006 19:37, Spitfire wrote:

These are the sequence of actions I performed in irb.

    class Dumber
        def sayHello
            puts "Hello!"
        end
    end
        db = Dumber.new()

    db.sayHello
    ## executes sayHello method!

    Class Dumber
        def sayHi
            puts "Hi"
        end
    end

    db.sayHi
    ## executes the newly added method sayHi!

  how does the object already created aware of the newly added method?

The method is added to it's *class* - and that relationship does not change, only the class changes.

It's class? I'm sorry I don't understand what you are saying. Can you please clarify?

--
_ _ _]{5pitph!r3}[_ _ _
__________________________________________________
“I'm smart enough to know that I'm dumb.”
   - Richard P Feynman

4

Robert Klemme wrote:

These are the sequence of actions I performed in irb.

    class Dumber
        def sayHello
            puts "Hello!"
        end
    end
        db = Dumber.new()

    db.sayHello
    ## executes sayHello method!

    Class Dumber
        def sayHi
            puts "Hi"
        end
    end

    db.sayHi
    ## executes the newly added method sayHi!

  how does the object already created aware of the newly added method?

The method is added to it's *class* - and that relationship does not change, only the class changes.

It's class? I'm sorry I don't understand what you are saying. Can you please clarify?

Sorry, should have read "its class". Please look closely at the IRB session to understand what I mean:

irb(main):001:0> class Foo
irb(main):002:1> def m1() end
irb(main):003:1> end
=> nil
irb(main):004:0> Foo.object_id
=> 1917050
irb(main):005:0> Foo.instance_methods.grep /m\d/
=> ["m1"]
irb(main):006:0> f=Foo.new
=> #<Foo:0x381468>
irb(main):007:0> f.class
=> Foo
irb(main):008:0> f.class.object_id
=> 1917050
irb(main):009:0> f.m1
=> nil
irb(main):010:0> f.m2
NoMethodError: undefined method `m2' for #<Foo:0x381468>
         from (irb):10
irb(main):011:0> class Foo
irb(main):012:1> def m2() end
irb(main):013:1> end
=> nil
irb(main):014:0> Foo.object_id
=> 1917050
irb(main):015:0> Foo.instance_methods.grep /m\d/
=> ["m2", "m1"]
irb(main):016:0> f.class
=> Foo
irb(main):017:0> f.class.object_id
=> 1917050
irb(main):018:0> f.m1
=> nil
irb(main):019:0> f.m2
=> nil

  robert

···

On 25.12.2006 20:44, Spitfire wrote:

On 25.12.2006 19:37, Spitfire wrote:

         from :0

5

Robert Klemme wrote:

Sorry, should have read "its class". Please look closely at the IRB session to understand what I mean:

irb(main):001:0> class Foo
irb(main):002:1> def m1() end
irb(main):003:1> end
=> nil
irb(main):004:0> Foo.object_id
=> 1917050
irb(main):005:0> Foo.instance_methods.grep /m\d/
=> ["m1"]
irb(main):006:0> f=Foo.new
=> #<Foo:0x381468>
irb(main):007:0> f.class
=> Foo
irb(main):008:0> f.class.object_id
=> 1917050
irb(main):009:0> f.m1
=> nil
irb(main):010:0> f.m2
NoMethodError: undefined method `m2' for #<Foo:0x381468>
        from (irb):10
        from :0
irb(main):011:0> class Foo
irb(main):012:1> def m2() end
irb(main):013:1> end
=> nil
irb(main):014:0> Foo.object_id
=> 1917050
irb(main):015:0> Foo.instance_methods.grep /m\d/
=> ["m2", "m1"]
irb(main):016:0> f.class
=> Foo
irb(main):017:0> f.class.object_id
=> 1917050
irb(main):018:0> f.m1
=> nil
irb(main):019:0> f.m2
=> nil

    robert

Sorry, didn't observe the IRB session closely. It's clear, now.

···

--
_ _ _]{5pitph!r3}[_ _ _
__________________________________________________
“I'm smart enough to know that I'm dumb.”
   - Richard P Feynman