Forum: Ruby Confusion with has object creation.

I know we create Hash object with Hash.new,it calls `initialize` method.

Here it is:

class Hash
  alias_method :_initialize, :initialize
  def initialize
     puts 'welcome!!'
     _initialize
  end
end
Hash.new #welcome

But how hash object is created when we call them as below:

Hash['a', 'b']
Hash['a' => 'b']

What method is being called internally?

Hash[] only call methods that you can not overwrite... it allocates the 
Hash without calling initialize.

Hash[obj] with only one argument does some kind of Magic too (because it 
trys to convert into an Hash and if that fails, try to convert into 
Array)

This is the method

http://www.ruby-doc.org/core-2.0/Hash.html#method-c-5B-5D

You can indeed overwrite it:

irb(main):001:0> class Hash
irb(main):002:1> def self.[](*args)
irb(main):003:2> {}
irb(main):004:2> end
irb(main):005:1> end
=> nil
irb(main):006:0> Hash['1','2']
=> {}

Hans Mackowiak wrote in post #1102398:
> Hash[] only call methods that you can not overwrite... it allocates the
> Hash without calling initialize.
>

Please give me one code example of this.I am heavily interested on it. I 
tried some code to see it,but not worked as I am looking for.

> Hash[obj] with only one argument does some kind of Magic too (because it
> trys to convert into an Hash and if that fails, try to convert into
> Array)

last time you used C functions to show me that i am Wrong and now you 
want C code? okay you get it:

when you do "show source" at 
http://www.ruby-doc.org/core-2.0/Hash.html#method-c-5B-5D you get this:

https://github.com/ruby/ruby/blob/trunk/hash.c#L389

please notice the: rb_hash_s_try_convert and rb_check_array_type

except for this ones the Hash[] function does not call ruby methods and 
only use the C representations of them, so overwriting them in ruby does 
not have any form of effect

Han s Mackowiak wrote in post #1102404:
> last time you used C functions to show me that i am Wrong and now you
> want C code? okay you get it:

No friend! I didn't challenge you, i will never do that even if I got 
grow up in ruby,rather I will try to convince him with the reality.:) 
Now I am not grown up so much in Ruby only 50% by concept, but I will 
try reach to 80%.

As far as I know I tried to show you my confusion areas, after that I 
drived into the source code with your hints and solved my confusion.

In this case,I am also looking into the source code,but didn't getting 
it as I am not getting function description of any function ruby till 
now,only code I got. within code to much functions are called. Those 
functions leading me to another confusion area, instead that if I got 
proper word description of each function,that could be better for me. 
like say a below.

My func(){
add(x,y) /* this function adds to number*/
}

Above kind of flavor I am not getting there. :) :)

> when you do "show source" at
> http://www.ruby-doc.org/core-2.0/Hash.html#method-c-5B-5D you get this:
>
> https://github.com/ruby/ruby/blob/trunk/hash.c#L389
>
> please notice the: rb_hash_s_try_convert and rb_check_array_type
>
> except for this ones the Hash[] function does not call ruby methods and
> only use the C representations of them, so overwriting them in ruby does
> not have any form of effect