[ruby-talk:01569] Re: Ruby: constructors, new and initialise

The following message is a courtesy copy of an article
that has been posted to comp.lang.misc as well.

Hi,

Dave Thomas <[e-mail]> writes:

|> some classes do not invoke `initialize' in their `new'
|> method.  They are Array, Regexp, IO (and its subclasses),
|> Hash, String, Thread, Class, and Module.  
|> # I'm feeling something left.

|Is this a performance thing? It seems like something of a surprise
|waiting to happen.

Two reasons:

  * performance, as you guessed.

  * these classes define their own version of `new' rather than using
    generic `new' defined in Object class.  these `new' methods
    use argument to allocate object, before calling `initialize' if any.

The latter is more significant.  The `initialize' trick works well
only if the arguments are used to initialize, not to allocate object.

For example, `new' of Array class uses its argument to determine
allocation size of internal buffer.  Calling `initialize' in the
method is useless, because meaning of an argument is already fixed.

I grad to hear if there's other good way to resolve it, preferably
being compatible.

							matz.