How can we create instance method and class methods at runtime in ruby?

ruby-talk
1

How can we create instance method and class methods at runtime in ruby?

class Foo
  def test
    p "hi"
  end
end
foo = Foo.new
foo.test # => "hi"
class Foo
  def test
    p "hiyy"
  end
end
foo.test
# >> "hi"
# >> "hiyy"

How Can I re-define the `test` method at runtime? I tried
`define_method`,but it didn't work for this.

···

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2

Don't know what you're doing, but this works:

$ irb
2.0.0p247 :001 > class Foo; def test; p "hi"; end;end
=> nil
2.0.0p247 :002 > foo = Foo.new
=> #<Foo:0x007fdef1882f20>
2.0.0p247 :003 > foo.test
"hi"
=> "hi"
2.0.0p247 :004 > class Foo; def test; p "bye"; end;end
=> nil
2.0.0p247 :005 > foo.test
"bye"
=> "bye"
2.0.0p247 :006 > class Foo; def self.test; p "bazinga!"; end;end
=> nil
2.0.0p247 :007 > Foo.test
"bazinga!"
=> "bazinga!"
2.0.0p247 :008 > foo.test
"bye"
=> "bye"

···

On Jul 22, 2013, at 11:43 PM, Love U Ruby <lists@ruby-forum.com> wrote:

How can we create instance method and class methods at runtime in ruby?

class Foo
def test
   p "hi"
end
end
foo = Foo.new
foo.test # => "hi"
class Foo
def test
   p "hiyy"
end
end
foo.test
# >> "hi"
# >> "hiyy"

How Can I re-define the `test` method at runtime? I tried
`define_method`,but it didn't work for this.

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

3

Sorry for creating the confusions:-

Here I tried once more to explain what I was looking for:

class Foo
  def test
    p "hi"
  end
end
foo = Foo.new
foo.test # => "hi"
Foo.define_method(:test){p "hello"}
# private method `define_method' called for Foo:Class (NoMethodError)

Any method is there to re-define the method `test` without re-opening
the class in runtime?

Thanks

···

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4

You can use class_eval:

Foo.class_eval do
  define_method(:test){p 'hello'}
end

or you can use send:

Foo.send :define_method, :test, &proc{p 'hello'}

I hope this helps

Stefano

···

On Tuesday 23 July 2013 Love U Ruby wrote

Sorry for creating the confusions:-

Here I tried once more to explain what I was looking for:

class Foo
  def test
    p "hi"
  end
end
foo = Foo.new
foo.test # => "hi"
Foo.define_method(:test){p "hello"}
# private method `define_method' called for Foo:Class (NoMethodError)

Any method is there to re-define the method `test` without re-opening
the class in runtime?

Thanks

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

5

Stefano Crocco wrote in post #1116318:

···

On Tuesday 23 July 2013 Love U Ruby wrote

Foo.class_eval do
  define_method(:test){p 'hello'}
end

or you can use send:

Foo.send :define_method, :test, &proc{p 'hello'}

I hope this helps

Stefano

Thanks @Stefano - this is what I was looking for.. :slight_smile:

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6

Be circumspect in doing this with define_method. It's a lot slower when you call the method:

···

On Jul 23, 2013, at 6:18 AM, Love U Ruby <lists@ruby-forum.com> wrote:

Stefano Crocco wrote in post #1116318:

On Tuesday 23 July 2013 Love U Ruby wrote

Foo.class_eval do
define_method(:test){p 'hello'}
end

or you can use send:

Foo.send :define_method, :test, &proc{p 'hello'}

I hope this helps

Stefano

Thanks @Stefano - this is what I was looking for.. :slight_smile:

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