[ nice-Bugs-930132 ] lazy initialization

Bugs item #930132, was opened at 2004-04-06 00:46
Message generated for change (Comment added) made by bsponline
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=112788&aid=930132&group_id=12788

Category: None
Group: None
>Status: Closed
Resolution: None
Priority: 5
Submitted By: Ka-Hing Cheung (bsponline)
Assigned to: Nobody/Anonymous (nobody)
Summary: lazy initialization

Initial Comment:
It's common to do this for lazy initialization:
?Blah blah = null;
if (blah == null)
    blah = new Blah();
blah.doThis();

However, this fails because the compiler thinks that
blah maybe null when you call blah.doThis().

If I declare blah as Blah (without ?), then the
compiler complains that I am comparing blah with null
(blah == null).

There should be a way to do this without using a
separate boolean variable to check if blah has been
initialized.

$ nice --version
Nice compiler version 0.9.6 (build 2004.03.05, 14:17:55
UTC)


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>Comment By: Ka-Hing Cheung (bsponline)
Date: 2004-04-06 04:25

Message:
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user_id=159910

Oops, it doesn't work on fields.

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Comment By: Ka-Hing Cheung (bsponline)
Date: 2004-04-06 02:37

Message:
Logged In: YES 
user_id=159910

This also fails:
?Blah blah;
then later:
return blah == null ? "N/A" : blah.getName();

This should also work, but I need to do this to get it to
compile:
return blah == null ? "N/A" : notNull(blah).getName();


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Comment By: Ka-Hing Cheung (bsponline)
Date: 2004-04-06 01:10

Message:
Logged In: YES 
user_id=159910

Okay, I now have a way to work around this:
Declare blah as usual:
?Blah blah = null;

Then later:
if (blah == null)
    blah = new Blah();
Blah tmp = notNull(blah);
tmp.doThis();

This works, but I think that's not very intuitive, as you
know that blah cannot be null already.

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Comment By: Ka-Hing Cheung (bsponline)
Date: 2004-04-06 00:59

Message:
Logged In: YES 
user_id=159910

A way to fix this would be, allow Blah blah to be compared
with null. That way I can modify the first line to:
Blah blah = cast(null);
And do not need to change anything else.

----------------------------------------------------------------------

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