Re^4: How to build a hash?

Sorry, maybe my use english is a bit confusing... 8-)
My problem was, I stored a reference to a hash (%hash_a) in a hash (%hash_b). Worked perfectly for one record.
Now, when i overwrote the contents of %hash_a, the contents in %hash_b where overwritten, too.
The whole stuff worked for more than one record only after I introduced the curly braces.

Comment on Re^4: How to build a hash?

Replies are listed 'Best First'.
Re^5: How to build a hash? by davorg (Chancellor) on Apr 26, 2005 at 15:16 UTC
There are two ways to take a reference to a hash. If you use the `\%hash` syntax then you are taking a reference to the _original_ hash. Any updates that you make through that reference will obviously update the original hash (as, actually, there is only ever one hash). If you use the `{ %hash }` syntax then you are creating a new anonymous hash which is a _copy_ of your original hash and getting a reference to this new hash. Any updates you make through this reference will update the copy of the hash and not the original hash. I recommend reading "perldoc perlreftut" and "perldoc perlref" to clarify these concepts. -- <http://www.dave.org.uk> "The first rule of Perl club is you do not talk about Perl club." -- Chip Salzenberg	[reply]

Replies are listed 'Best First'.

Re^5: How to build a hash?
by davorg (Chancellor) on Apr 26, 2005 at 15:16 UTC

There are two ways to take a reference to a hash.

If you use the \%hash syntax then you are taking a reference to the _original_ hash. Any updates that you make through that reference will obviously update the original hash (as, actually, there is only ever one hash).

If you use the { %hash } syntax then you are creating a new anonymous hash which is a _copy_ of your original hash and getting a reference to this new hash. Any updates you make through this reference will update the copy of the hash and not the original hash.

I recommend reading "perldoc perlreftut" and "perldoc perlref" to clarify these concepts.

--
<http://www.dave.org.uk>

"The first rule of Perl club is you do not talk about Perl club."
-- Chip Salzenberg

[reply]