what's difference between bless and tie?

[Anonymous Monk]

bless will bind a data structure to a package name; When I read tie, it seems also bind a data to something. can someone please explain to me their difference? Thanks!

[moritz]

bless allows you to calls methods on the blessed object.

tie allows you to override built-in operations on variables, namely reading from/assigning to scalars, and list and hash operations like indexing, exists, delete etc.

So in some sense, tie works on a variable and bless works on a thing that is stored in a variable.

[anaconda_wly]

"bless allows you to calls methods on the blessed object." , and "the blessed object" actually a data structure saying a hash and bless tells Perl how the hash can be used(methods defined in package). I still feel they're hard to distinguish in their very initial goal.

[BrowserUk]

With tie you bless a named variable, and a predefined set of methods for that variable type are called automatically as the variable is used.

It allows the variables to be used exactly as if they were normal Perl variables of that type rather than requiring the methods be called using object syntax, which makes for very natural usage:

tie my @array, 'Some::Thing';

...

$array[ $n ] *= 5;

Rather than the clumsy:

my $myObj  = Some::Thing->new();
...

$myObj->setItem( $n, $myObj->getItem( $n ) * 5 );

[ww]

Did you read perldoc -f bless and perldoc -f tie?

The documents (as usual) have a few hints.

[LanX]

good question, but so frequently asked that all good answers were already given!

googling the monastery

supersearching (klick search)

general googling

Still any questions left?

[anaconda_wly]

Thank you all for the wonderful reply. All replies are what I wanted: concise and by analogy. Sorry for late thanks as the New Year holiday. Frankly to say I didn't catch the answers all yet. But I'll read more as LanX suggested and then read your words again before any further question. Thanks and Happay new year!