Automatically call class method in objective c

my situation:

• a dashboard controller who register the widgets inside it and automatically builds the view.

• widget classes that are going to populate the dashboard, who adopt <widget> protocol(some informal methods required), and need to be registered in the dashboard class so the dashboard singleton knows who wants to be in.

• the dashboard class has +(void)register:(Class<widget>)w; that simply register the classes 开发者_如何转开发who wants to be in in an NSArray

I need each widget class to call automatically that method.in c++ i used to make a boolean static variable that i would initialize with that method. Language = objective-c

The objective-c runtime will call two methods when a class is first loaded. +load and +initialize. I believe what you want could be done by calling [self register] from within +initialize.

A way you could do it is with the runtime:

1. Grab a list of all the classes known to the runtime.
2. Iterate the list, and check to see if the class conforms to your widget protocol
3. If it does conform to the protocol, invoke the +register: method or whatever

Regarding step #2, you can't use the +conformsToProtocol: method, because one of the classes you'll iterate is the NSZombie class, which triggers an exception whenever you invoke a method on it. Thus, you'd want to use the class_conformsToProtocol() runtime function instead.