From: Rick DeNatale <rick.denatale@...>
Date: 2009-04-02T03:24:56+09:00
Subject: Re: Anything better than klass = eval("#{task_class}")

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On Wed, Apr 1, 2009 at 12:37 PM, Rob Biedenharn
<Rob@agileconsultingllc.com>wrote:

>
> On Apr 1, 2009, at 12:09 PM, Rick DeNatale wrote:
>
>  On Wed, Apr 1, 2009 at 10:47 AM, Rob Biedenharn
>> <Rob@agileconsultingllc.com>wrote:
>>
>>  On Apr 1, 2009, at 9:32 AM, Gregory Brown wrote:
>>>
>>> On Wed, Apr 1, 2009 at 9:14 AM, Paganoni <noway@fakenullvoid.com> wrote:
>>>
>>>>
>>>>  Hi, well subject is self explanatory...
>>>>>
>>>>> Seems a bit to verbose for me but I don't know any other solution to
>>>>> convert
>>>>> a string containing a class name to a constant of that class name...
>>>>> Excepted rails way : task_class.camelize.constantize which is verbose
>>>>> too...
>>>>>
>>>>>
>>>> Object.const_get("String")
>>>>
>>>>>
>>>>>>  => String
>>>>>
>>>>
>>>> -greg
>>>>
>>>> --
>>>> BOOK:  http://rubybestpractices.com
>>>> TECH: http://blog.majesticseacreature.com
>>>> NON-TECH: http://metametta.blogspot.com
>>>>
>>>>
>>> Or dealing with things like Admin::User or Net::HTTP
>>>
>>> # from Jim Weirich (based on email correspondence)
>>> def constantize(camel_cased_word)
>>>  camel_cased_word.
>>>    sub(/^::/,'').
>>>    split("::").
>>>    inject(Object) { |scope, name| scope.const_get(name) }
>>> end
>>>
>>> It may be more verbose, but it is much safer that plain 'ole eval()
>>>
>>>
>> Actually, I don't think this is entirely right, since const_get will find
>> constants found in outer scopes.
>>
>> For example constantize("MyModule::Object") would return ::Object
>>
>> So a little better would be:
>>
>> def constantize(camel_cased_word)
>>  camel_cased_word.
>>    sub(/^::/,'').
>>    split("::").
>>    inject(Object) { |scope, name| scope.const_defined?(name) ?
>> scope.const_get(name) : scope.const_missing(name) }
>> end
>>
>> Except for the slight difference in the backtrace, it looks the same to
> me. Why do you think it will return Object for
> constantize("MyModule::Object") ?


Because it does, if MyModule is actually defined and doesn't define another
inner constant called Object:

def constantize(camel_cased_word)
  camel_cased_word.

  sub(/^::/,'').
  split("::").
  inject(Object) { |scope, name| scope.const_get(name) }
end


module MyModule
end

constantize("MyModule::Object") # => Object

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