From: Day <iamday@...>
Date: 2008-02-09T13:52:22+09:00
Subject: Re: info on block arguments

On Feb 8, 2008 10:22 PM, Russell Me <russ@geekwhiz.com> wrote:
> So, after 3 days I still don't understand this. Is it really that
> difficult, or am i just plain dumb?

It is not exactly a simple concept. Especially, I think, if you're not
familiar with object oriented thinking.

> While I'm looking to understand the kitty_toys sort, it's really just
> because I want to know how it all works.

I think, actually, that _why's example is pretty complex, so maybe it
would be better for stick with your 3.times example.

> even this:
> 3.times {|x| puts x }
>
> I see it work, I understand what's going on, but I don't know HOW it's
> working.

Actually. Maybe let's make it simpler. Forget, for the moment, about
the |x| bit. Let's look at this code:

3.times { puts "Arr!" } # Very high seas.

The block, there, is sort of where you store code for a second. So you
wrap up something to be executed (the puts statement in this case) in
a block and you hand it to the times method. Not every method can
accept a block like that, but this one can.

So what the times method does is it executes whatever's in the block
it got handed a number of times equal to the integer it was called on
(three in this case). It sort of says, in English:
Do 'puts "Arr!"' three times.

If you're entirely new to OOP, it may be hard to remember or envision
this, but: The code does not execute in sequence. Remember that 3 is
an object. It is doing something (the method). It can do that thing,
on stuff that you hand it (a block in this case, but this is true for
all arguments). Really, the key difference between a block and any
other argument you might pass to a method is that a block is code that
can be executed, but the execution is held off until the method it's
passed to asks it to execute.

Does that make some sense? If you get that alright, then I think it'll
be a bit easier to move on to the more complicated examples. Kudos, by
the way, for your perseverence. Lesser men would have given up in
frustration by now. I hope you don't feel like you're being badgered
or yelled at or ganged up on. Hang in there. You'll get it.


Ben