Add a variable to a class instance at runtime: Difference between revisions
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=={{header|Objective-C}}== |
=={{header|Objective-C}}== |
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Objective-C doesn't have the ability to add a variable to an instance at runtime. However, since Mac OS X 10.6 and iOS 3.1, it has something that can accomplish a very similar purpose, called "associative references" or "associated objects", which allow you to attach additional |
Objective-C doesn't have the ability to add a variable to an instance at runtime. However, since Mac OS X 10.6 and iOS 3.1, it has something that can accomplish a very similar purpose, called "associative references" or "associated objects", which allow you to attach additional objects onto an object without changing its class. |
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You can put associative references on any object. You can put multiple ones on the same object. They are indexed by a pointer key (typically the address of some dummy variable). You use the functions <code>objc_getAssociatedObject()</code> and <code>objc_setAssociatedObject</code> to get and set them, respectively. |
You can put associative references on any object. You can put multiple ones on the same object. They are indexed by a pointer key (typically the address of some dummy variable). You use the functions <code>objc_getAssociatedObject()</code> and <code>objc_setAssociatedObject</code> to get and set them, respectively. |
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