Robert Cummings wrote:
Richard Quadling wrote:
Hi.
I have a scenario where I would _like_ to have multiple constructors
for a class.
Each constructor has a greater number of parameters than the previous one.
e.g.
<?php
class myClass {
__construct(string $Key) // use key to get the complex details.
__construct(string $Part1, string $Part2, string $Part3) //
Alternative route to the complex details.
__construct(array $Complex) // All the details
}
Essentially, SimpleKey is a key to a set of predefined rules. Part1, 2
and 3 are the main details and well documented defaults for the rest
of the rules. Complex is all the rules.
Each constructor will end up with all the parts being known ($Key,
$Part1, $Part2, $Part3, $Complex).
But, PHP doesn't support multiple constructors.
Initially I thought about this ...
__construct($Key_Part1_Complex, $Part2=Null, $Part3=Null)
But then documenting the first param as being 1 of three different
meanings is pretty much a no go.
So I'm looking for a clean and easily understood way to provide this.
I won't be the only user of the code and not everyone has the same
knowledge level, hence a mechanism that is easily documentable.
I think I may need a factory with multiple methods (FactoryKey,
FactoryPart1To3, FactoryComplex). Make the factory a static/singleton.
All these methods eventually call the real class with the complex
rule.
Is that obvious enough?
Factory method is probably the cleanest and simplest solution. Just pass
an ID as the first parameter to the real constructor and then it can
route to the appropriate behaviour:
Here's a better example (tested):
<?php
class Foo
{
const CONSTRUCT_BLAH = 1;
const CONSTRUCT_BLEH = 2;
const CONSTRUCT_BLUH = 3;
function __construct( $constructId )
{
static $map = array
(
self::CONSTRUCT_BLAH => '__construct_blah',
self::CONSTRUCT_BLEH => '__construct_bleh',
self::CONSTRUCT_BLUH => '__construct_bluh',
);
$obj = null;
if( isset( $map[$constructId] ) )
{
$args = func_get_args();
$args = array_shift( $args );
call_user_func_array(
array( 'self', $map[$constructId] ), $args );
}
else
{
// Generate an error or exception.
}
}
static function __construct_bleh( $arg1 )
{
echo "Called: ".__FUNCTION__."( $arg1 )\n";
}
static function __construct_blah( $arg1 )
{
echo "Called: ".__FUNCTION__."( $arg1 )\n";
}
static function __construct_bluh( $arg1 )
{
echo "Called: ".__FUNCTION__."( $arg1 )\n";
}
static function getBlah( $arg1 )
{
return new Foo( self::CONSTRUCT_BLAH, $arg1 );
}
static function getBleh( $arg1 )
{
return new Foo( self::CONSTRUCT_BLEH, $arg1 );
}
static function getBluh( $arg1 )
{
return new Foo( self::CONSTRUCT_BLUH, $arg1 );
}
}
$obj = Foo::getBlah( 'blah' );
$obj = Foo::getBleh( 'bleh' );
$obj = Foo::getBluh( 'bluh' );
?>
Cheers,
Rob.
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