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Request #66012 "initialize" keyword allowing member caching
Submitted: 2013-10-31 15:26 UTC Modified: 2013-10-31 16:59 UTC
From: llmll at gmx dot de Assigned:
Status: Wont fix Package: Variables related
PHP Version: Irrelevant OS: any
Private report: No CVE-ID: None
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 [2013-10-31 15:26 UTC] llmll at gmx dot de
Description:
------------
PHP should provide a method to initialize (static or instance) members of objects and later present cached data.

Motivation is to hide the program logic for first-time fetching of data, which is important for ORM classes.

$Property gets a new keyword "initialize" and a block, which is executed if and only if $Property === null. The called blocks returns a value, that is onwards stored in this property. Subsequent calls just return the value.

So the return value is cached! The cached value can later be cleared, just by setting $Property = null;

This keyword also candidates for static property initializers!

Thanks for reading and thinking.

Test script:
---------------
class Foo {
    public $BigData;

    public function InitializeBigData() {
        // this has to be called somehwere
        // and tends to get forgotten
        // or calle to late, after some code
        // accesses $BigData directly and hits null

        $this->BigData = somehow::getBigData();
    }

    public function GetBigData() {
        // smarter method, but must be called every time
        // when you want to access BigData
        // but is not a property
        // too much writing overhead for many properties

        if ($this->BigData === null) {
            $this->BigData = somehow::getBigData();
        }
        return $this->BigData;
    }
}

Expected result:
----------------
class Foo {
    public $BigData initialize {
        // this block gets executed only, if property is null
        // fetches big data and stores it internally somewhere
        return somehow::getBigData();
    }
}

$foo = new Foo();

// don't care about BigData being read or cached, its just there.
echo $foo->BigData;

// reset cached value
$foo->BigData = null;

// will load BigData again
echo $foo->BigData;


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 [2013-10-31 16:59 UTC] johannes@php.net
-Status: Open +Status: Wont fix
 [2013-10-31 16:59 UTC] johannes@php.net
You can easily do this in a constructor, actually this is what a constructor is for. Extneding the language for this makes the language more complex, causes issues with execution order, error handling and probably other things which you now can handle.
 
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