Daniel Schüle
10/23/2006 11:42:00 AM
Robert Klemme schrieb:
> Brad Tilley wrote:
>> What exactly is the difference between these? :: is a class method
>> while is an instance method??? If that is so, could someone clarify
>> this with more detail? I use File.open, but File::open works too.
>
> The same method (a class method) is called. It is just a syntactic
> difference. So these are the same
>
> File.open("foo") ...
> File::open("foo") ...
>
> > However
>> sometimes, this is not the case which adds to my confusion :) For
>> example, I can only do Digest::MD5.new() and not Digest.MD5.new() why
>> is that?
>
> Because the "." cannot be used for constant lookup:
>
> irb(main):005:0> File.NONBLOCK
> NoMethodError: undefined method `NONBLOCK' for File:Class
> from (irb):5
> from :0
> irb(main):006:0> File::NONBLOCK
> => 16384
>
> "." is reserved for method invocations.
>
>> I don't fully understand OO programming... perhaps this is my problem.
>
> Nah, I think it is rather a minor ambiguity in the language that causes
> confusion. Usually people disambiguate it by using "." for methods and
> "::" for constants only although they could use it for class methods as
> well.
I was bitten by it more than once
is there more to it ... i mean ambiguity is usually not what one wants
to have in the language (at least not in the computer language :-)
Regards, Daniel