| Recipe 1.14: Determining the Existence of an Attribute or Method |
Last Updated: Sep 8, 2003
Status: Draft
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Problem:
You have a class name or an object of unknown type. You want to find out whether or not a foo attribute or method exists in that class or object.
Solution:
Use the CAN method, made available to every perl6 class:
MyClass.CAN('foo'); # on a class
if ($obj.CAN('foo')) { # on an object
$obj.foo;
}
MyClass can 'foo'; # "can" operator; synonymous
$obj can 'foo';
Discussion:
The CAN method takes a name and returns a boolean value indicating whether or not the given object or class has an attribute or method by that name. This allows you to determine if an object has a given capability, without caring what the actual definition of the object may be.
As a shorthand version, the "can" operator functions in a similar manner: given a class name or an object on the left side, it returns whether that class or object has the attribute or method named on the right side.
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