CODEWITHSUNDEEP
actionscript-3flashreflectionactionscriptruntime
spierepf
spierepf

Reputation: 2944

How to determine if a Class object represents a class or an interface in actionscript 3.0

I am trying to develop a method in actionscript that takes a Class object as a parameter and will generate an instance of that class at runtime:

public function getComponent(componentType:Class):Object
{
    return new componentType();
}

In some cases I may be passed a Class object that represents an interface instead. Naturally I cannot directly create an instance of an interface.

Is there some way to query the Class object and determine whether or not it represents an interface so that I can avoid trying to create an instance in this way?

Upvotes: 1

Views: 91

Answers (3)

Andrey Popov
Andrey Popov

Reputation: 7520

I think this will work for you:

getQualifiedSuperclassName(classObject);

This will return null if you pass an interface, as interfaces does not have a superclass. It will always give you ANY kind of result for a class, as every class is basically an Object :)

Anyway, I don't think that passing such mixed values to a function is a good idea ;) And checking if the class starts with "I" is worse (sorry Bennett :))

p.s. Keep in mind that describeType is EXTREMELY slow!

Upvotes: 1

spierepf
spierepf

Reputation: 2944

After some careful trial and error, I've come up with the following function:

public static function isInterface(clazz:Class):Boolean
{
    return describeType(clazz).factory.extendsClass.(@type=="Object").length()==0;
}

Does anyone know if this condition always holds true for all actionscript interfaces?

Upvotes: 1

Bennett Keller
Bennett Keller

Reputation: 1714

Assume you follow a naming convention for your interface class, as in the standard IInterfaceName, name of the interface prefixed with a capital "I" following a capital letter and the rest of the class name. There are a couple of ways to do this. If you have a lot of different interfaces that could be passed as a parameter you could do this:

First import the flash.utils.getQualifiedClassName and in your function:

public function getComponent(componentType:Class):Object
{
    var name:String = getQualifiedClassName( componentType ).replace(/.*\:+/g,"");
    if ( name.search( /^\I[A-Z]/g ) != -1 ) {
        trace( "parameter is an interface!" );
        return null;
    }
    return new componentType();
}

You don't have to set the name variable, but this helps make the search a little more strict. You could just do this instead:

if ( getQualifiedClassName( componentType ).search( /\I[A-Z]/g ) != -1 ) {
    trace( "parameter is an interface!" );
    return null;
}

If you are not already aware, getQualifiedClassName returns the string format of the class name. The regular expressions check specifically for the capital IInterfaceName styled string.

Lastly, if you know it's only one interface, you could simple just do this:

if ( componentType == IMyinterface ) {
    trace( "component is a IMyinterface" );
}

Upvotes: 1

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