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where does the pure method defined when starting irb

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  where does the pure method defined when starting irb Brian Xue <brxue.cn@gmail.com> - 2011-05-12 04:40 -0500
    Re: where does the pure method defined when starting irb jake kaiden <jakekaiden@yahoo.com> - 2011-05-12 06:17 -0500
    Re: where does the pure method defined when starting irb Christopher Dicely <cmdicely@gmail.com> - 2011-05-12 09:57 -0500
      Re: where does the pure method defined when starting irb Michael Edgar <adgar@carboni.ca> - 2011-05-12 10:12 -0500
      Re: where does the pure method defined when starting irb 7stud -- <bbxx789_05ss@yahoo.com> - 2011-05-12 14:00 -0500
        Re: where does the pure method defined when starting irb Brian Xue <brxue.cn@gmail.com> - 2011-05-12 18:57 -0500
          Re: where does the pure method defined when starting irb 7stud -- <bbxx789_05ss@yahoo.com> - 2011-05-12 21:07 -0500
            Re: where does the pure method defined when starting irb Brian Xue <brxue.cn@gmail.com> - 2011-05-16 19:54 -0500
              Re: where does the pure method defined when starting irb Michael Edgar <adgar@carboni.ca> - 2011-05-16 20:00 -0500
                Re: where does the pure method defined when starting irb Brian Xue <brxue.cn@gmail.com> - 2011-05-16 21:24 -0500
        Re: where does the pure method defined when starting irb 7stud -- <bbxx789_05ss@yahoo.com> - 2011-05-12 18:58 -0500
    Re: where does the pure method defined when starting irb 7stud -- <bbxx789_05ss@yahoo.com> - 2011-05-12 13:21 -0500
    Re: where does the pure method defined when starting irb 7stud -- <bbxx789_05ss@yahoo.com> - 2011-05-12 13:53 -0500

#4344 — where does the pure method defined when starting irb

[Note:  parts of this message were removed to make it a legal post.]

Hello,

I have some puzzles, when I start irb,

puts self
=> main
puts self.class
=> Object

After that, if I write the following method,

def hello; end
=>nil

then where is the method "hello" defined? within Object? but

self.class.instance_methods.include? :hello
=>false

Can anyone help explain that?

Thanks in advance!

Brian

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#4345

hi -

  try this:


irb(main):001:0> def hello; end

irb(main):002:0> self.public_methods.include?("hello")
=> true

 cheers,

  -j

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

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#4371

On Thu, May 12, 2011 at 2:40 AM, Brian Xue <brxue.cn@gmail.com> wrote:
> Hello,
>
> I have some puzzles, when I start irb,
>
> puts self
> => main
> puts self.class
> => Object
>
> After that, if I write the following method,
>
> def hello; end
> =>nil
>
> then where is the method "hello" defined? within Object? but
>
> self.class.instance_methods.include? :hello
> =>false

Right, because its not defined as an instance method in the Object
class, its defined as an instance method in the singleton class of the
current object (main).

So, in IRB for Ruby 1.8.7 after the above

(class <<self; end).instance_methods.include? "hello"
=> true

For some reason, IRB for Ruby 1.9.2 is weird, and I can't find the
method anywhere, even though the method works. Even respond_to?
ignores it:

ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux]
christopher@ubuntu:~$ irb
ruby-1.9.2-p180 :001 > def hello
ruby-1.9.2-p180 :002?>   "hello"
ruby-1.9.2-p180 :003?>   end
 => nil
ruby-1.9.2-p180 :004 > hello
 => "hello"
ruby-1.9.2-p180 :005 > self.respond_to? :hello
 => false

Its back to working again in head, which shows the cleaner 1.9 syntax:

christopher@ubuntu:~$ ruby -v
ruby 1.9.3dev (2011-05-02 trunk 31407) [x86_64-linux]
christopher@ubuntu:~$ irb
ruby-head :001 > def hello
ruby-head :002?>   "hello"
ruby-head :003?>   end
 => nil
ruby-head :004 > hello
 => "hello"
ruby-head :005 > self.respond_to? :hello
 => true
ruby-head :006 > self.singleton_class.instance_methods.include? :hello
 => true

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#4375

[Note:  parts of this message were removed to make it a legal post.]

On May 12, 2011, at 10:57 AM, Christopher Dicely <cmdicely@gmail.com> wrote:

On Thu, May 12, 2011 at 2:40 AM, Brian Xue <brxue.cn@gmail.com> wrote:

Hello,


I have some puzzles, when I start irb,


puts self

=> main

puts self.class

=> Object


After that, if I write the following method,


def hello; end

=>nil


then where is the method "hello" defined? within Object? but


self.class.instance_methods.include? :hello

=>false


Right, because its not defined as an instance method in the Object
class, its defined as an instance method in the singleton class of the
current object (main).

So, in IRB for Ruby 1.8.7 after the above

(class <<self; end).instance_methods.include? "hello"
=> true

For some reason, IRB for Ruby 1.9.2 is weird, and I can't find the
method anywhere, even though the method works. Even respond_to?
ignores it:

ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux]
christopher@ubuntu:~$ irb
ruby-1.9.2-p180 :001 > def hello
ruby-1.9.2-p180 :002?>   "hello"
ruby-1.9.2-p180 :003?>   end
=> nil
ruby-1.9.2-p180 :004 > hello
=> "hello"
ruby-1.9.2-p180 :005 > self.respond_to? :hello
=> false

Its back to working again in head, which shows the cleaner 1.9 syntax:

christopher@ubuntu:~$ ruby -v
ruby 1.9.3dev (2011-05-02 trunk 31407) [x86_64-linux]
christopher@ubuntu:~$ irb
ruby-head :001 > def hello
ruby-head :002?>   "hello"
ruby-head :003?>   end
=> nil
ruby-head :004 > hello
=> "hello"
ruby-head :005 > self.respond_to? :hello
=> true
ruby-head :006 > self.singleton_class.instance_methods.include? :hello
=> true


Methods defined at the top level are created as a private instance method on
the Object class. You can use public/private at the top level to change the
visibility used. In this case, try Object.private_instance_methods(false) .

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#4414

Christopher Dicely wrote in post #998250:
> On Thu, May 12, 2011 at 2:40 AM, Brian Xue <brxue.cn@gmail.com> wrote:
>>
>> def hello; end
>> =>nil
>>
>> then where is the method "hello" defined? within Object? but
>>
>> self.class.instance_methods.include? :hello
>> =>false
>
> Right, because its not defined as an instance method in the Object
> class, its defined as an instance method in the singleton class of the
> current object (main).
>
> So, in IRB for Ruby 1.8.7 after the above
>
> (class <<self; end).instance_methods.include? "hello"
> => true
>

Also:

puts RUBY_VERSION

x = class A
end

p x

x  = class <<self
end

p x

--output:--
1.9.2
nil
nil


===

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

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#4442

[Note:  parts of this message were removed to make it a legal post.]

Thanks all for your kindly explanation. It really helps.

Brian

2011/5/13 7stud -- <bbxx789_05ss@yahoo.com>

> Christopher Dicely wrote in post #998250:
> > On Thu, May 12, 2011 at 2:40 AM, Brian Xue <brxue.cn@gmail.com> wrote:
> >>
> >> def hello; end
> >> =>nil
> >>
> >> then where is the method "hello" defined? within Object? but
> >>
> >> self.class.instance_methods.include? :hello
> >> =>false
> >
> > Right, because its not defined as an instance method in the Object
> > class, its defined as an instance method in the singleton class of the
> > current object (main).
> >
> > So, in IRB for Ruby 1.8.7 after the above
> >
> > (class <<self; end).instance_methods.include? "hello"
> > => true
> >
>
> Also:
>
> puts RUBY_VERSION
>
> x = class A
> end
>
> p x
>
> x  = class <<self
> end
>
> p x
>
> --output:--
> 1.9.2
> nil
> nil
>
>
> ===
>
> --
> Posted via http://www.ruby-forum.com/.
>
>

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#4455

Brian Xue wrote in post #998397:
> Thanks all for your kindly explanation. It really helps.

Here's more:

class Object
  private

  def greet
    puts 'hello'
  end
end

class B
end

puts Object.private_instance_methods.include?(:greet)
puts B.private_instance_methods.include?(:greet)
puts self.singleton_class.private_instance_methods.include?(:greet)

not_inherited = false
puts 
self.singleton_class.private_instance_methods(not_inherited).include?(:greet)


--output:--
true
true
true
false

The lookup paths:

Object
  ^ private :greet
  |
  |
Class B
  ^
  |
  |
singleton class of b
  ^
  |
  |
b = B.new





Object
  ^ private :greet
  |
  |
singleton class of 'main'
  ^
  |
  |
 main


You really can't determine in which class a method is defined unless you 
call the *_methods() with false as the argument, which causes ruby to 
ignore inherited methods.

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

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#4649

[Note:  parts of this message were removed to make it a legal post.]

Thank you all.

Here I have another similar question:

puts self
=> main
def hello;
@v = 1;
end
=>nil

then I assume @v should be an instance variable of 'main', but

puts self.instance_variables
=>nil

Can anyone help explain?

Many thanks!

Brian

On Fri, May 13, 2011 at 10:07 AM, 7stud -- <bbxx789_05ss@yahoo.com> wrote:

> Brian Xue wrote in post #998397:
> > Thanks all for your kindly explanation. It really helps.
>
> Here's more:
>
> class Object
>  private
>
>  def greet
>    puts 'hello'
>  end
> end
>
> class B
> end
>
> puts Object.private_instance_methods.include?(:greet)
> puts B.private_instance_methods.include?(:greet)
> puts self.singleton_class.private_instance_methods.include?(:greet)
>
> not_inherited = false
> puts
>
> self.singleton_class.private_instance_methods(not_inherited).include?(:greet)
>
>
> --output:--
> true
> true
> true
> false
>
> The lookup paths:
>
> Object
>  ^ private :greet
>  |
>  |
> Class B
>  ^
>  |
>  |
> singleton class of b
>  ^
>  |
>  |
> b = B.new
>
>
>
>
>
> Object
>  ^ private :greet
>  |
>  |
> singleton class of 'main'
>  ^
>  |
>  |
>  main
>
>
> You really can't determine in which class a method is defined unless you
> call the *_methods() with false as the argument, which causes ruby to
> ignore inherited methods.
>
> --
> Posted via http://www.ruby-forum.com/.
>
>

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#4651

An instance variable doesn't get created until it is first assigned. So in this case, you
have to call `hello` before @v will show up in `self.instance_variables`:

puts self
=> main
def hello
@v = 1
end
=> nil
puts self.instance_variables
=> nil
hello
=> 1
puts self.instance_variables
=> @v
=> [:@v]

Michael Edgar
adgar@carboni.ca
http://carboni.ca/

On May 16, 2011, at 8:54 PM, Brian Xue wrote:

> Can anyone help explain?
> 
> Many thanks!
> 
> Brian

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#4652

[Note:  parts of this message were removed to make it a legal post.]

Thank you very much, Michael!

Brian

On Tue, May 17, 2011 at 9:00 AM, Michael Edgar <adgar@carboni.ca> wrote:

> An instance variable doesn't get created until it is first assigned. So in
> this case, you
> have to call `hello` before @v will show up in `self.instance_variables`:
>
> puts self
> => main
> def hello
> @v = 1
> end
> => nil
> puts self.instance_variables
> => nil
> hello
> => 1
> puts self.instance_variables
> => @v
> => [:@v]
>
> Michael Edgar
> adgar@carboni.ca
> http://carboni.ca/
>
> On May 16, 2011, at 8:54 PM, Brian Xue wrote:
>
> > Can anyone help explain?
> >
> > Many thanks!
> >
> > Brian
>
>
>

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#4445

7stud -- wrote in post #998328:
>
> Also:
>
> puts RUBY_VERSION
>
> x = class A
> end
>
> p x
>
> x  = class <<self
> end
>
> p x
>
> --output:--
> 1.9.2
> nil
> nil
>
>
> p x.instance_methods
>
> prog.rb:11:in `<main>': undefined method `instance_methods' for
> nil:NilClass (NoMethodError)


And...

puts RUBY_VERSION  #=>1.8.6

x = class A
end

p x    #=>nil

x  = class <<self
end

p x    #=>nil

p x.instance_methods  #error

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

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#4403

puts RUBY_VERSION

puts self       #=>main
puts self.class #=>Object

def hello
end

puts Object.private_methods.grep(/^h/) #=>hello

puts self.singleton_class.instance_methods.include?(:hello)
#=>false

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

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#4412

Also:

puts RUBY_VERSION  #=>1.8.6

puts self       #=>main
puts self.class #=>Object

def hello
end

puts Object.private_instance_methods.grep(/^h/) #=>hello

puts self.public_methods.include?("hello")
#=>false

#puts self.singleton_class.instance_methods.include?(:hello)

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

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