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Re: Blocks for scope control

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On 15.01.2012 22:49, Arved Sandstrom wrote:
> On 12-01-15 03:00 PM, Lew wrote:
>>   Arved Sandstrom wrote:
>> You see it standardly in initialization blocks, especially static,
>> though I often (more often than not) find myself refactoring static
>> initialization blocks to private static methods.  For instance
>> initialization they're extremely useful for blocks that multiple
>> constructors must share.
>
> At the instance and class levels, it's true, these blocks operate
> similarly to "local" blocks.

That's also a feature I use from time to time.  But I thought this 
discussion was more about blocks inside methods since initializer blocks 
are a quite different beast (you can view them as anonymous methods 
without arguments and return type).

>> Within methods I use them as well, to enforce temporariness of
>> variables. This is very handy to prevent re-use of a variable whose
>> usefulness has expired.  The need is rare, but like the legendary
>> left-handed stembolt, if you don't have it when you need it, that's a
>> worry.
>
> This is exactly the use I was calling out. After visibility modifiers we
> then have a number of levels of scope - class, instance, method and
> block. We already use restrictive variable scoping in blocks; everyone
> who re-uses for-loop index names benefits from this.
>
> My point is simply that on some occasions, as you point out yourself,
> you do want to "enforce temporariness" of a variable in a scope narrower
> than that of its enclosing method. The answer here, on those infrequent
> occasions where it makes sense to use a block, is not to blindly create
> a new method simply to get variable scoping. That reflexive practice can
> lead to unreadable fragmented code.

But there are other blocks which also restrict scope (i.e. flow 
control).  So more often than not I find myself using those.  Plus, I 
now have made it a habit to make variables final as often as possible 
(mostly for documentation reasons) and thusly also prevent accidental reuse.

Regarding the method refactoring argument: if there is so much code and 
hence so many local variables that you want to use blocks to introduce 
smaller scopes chances are that the logic within that blocks is also 
largely independent from the code around so it is a good candidate for 
refactoring anyway.  The reason for refactoring into methods isn't the 
scope but the independent logic.

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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Thread

Blocks for scope control Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-15 11:50 -0400
  Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-15 17:10 +0100
  Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-15 17:32 +0100
    Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-15 11:21 -0800
    Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-16 07:59 +0100
  Re: Blocks for scope control markspace <-@.> - 2012-01-15 09:57 -0800
    Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-15 11:28 -0800
  Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-15 11:00 -0800
    Re: Blocks for scope control Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-15 17:49 -0400
      Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-15 15:45 -0800
        Re: Blocks for scope control Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-19 21:54 -0400
          Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-20 08:41 +0100
            Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-20 15:24 -0800
            Re: Blocks for scope control Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-20 19:30 -0400
              Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-20 15:54 -0800
      Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-16 07:55 +0100
        Re: Blocks for scope control Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-19 21:16 -0400
          Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-21 13:25 +0100
            Re: Blocks for scope control Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-21 10:41 -0400
              Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-22 13:03 +0100
  Re: Blocks for scope control Roedy Green <see_website@mindprod.com.invalid> - 2012-01-16 06:09 -0800
    Re: Blocks for scope control Henk van Voorthuijsen <voorth@xs4all.nl> - 2012-01-16 07:03 -0800
  Re: Blocks for scope control Arne Vajhøj <arne@vajhoej.dk> - 2012-01-17 18:43 -0500
  Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-20 11:05 -0800
  Re: Blocks for scope control Gene Wirchenko <genew@ocis.net> - 2012-01-20 12:11 -0800
  Re: Blocks for scope control Arne Vajhøj <arne@vajhoej.dk> - 2012-02-06 21:24 -0500

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