Dynamic changes!

Ruby
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?

2

On 25.12.2006 19:37, Spitfire wrote:

db.sayHello

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.

$ 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
3

Robert K. wrote:

db.sayHello

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?

4

On 25.12.2006 20:44, Spitfire wrote:

## 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
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