Automatically call class method in objective c

Question

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 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

please use proper formatting.

vikingosegundo
– vikingosegundo

2011-09-28 17:25:35 +00:00
Commented Sep 28, 2011 at 17:25 — vikingosegundo
– vikingosegundo, Commented Sep 28, 2011 at 17:25

Dave DeLong · Accepted Answer · 2011-09-28 17:20:02Z

2

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.

edited Sep 28, 2011 at 17:20

Dave DeLong

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answered Sep 28, 2011 at 15:32

Joshua Weinberg

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8 Comments

ughoavgfhw Over a year ago

+initialize is only called when the class is used, not when it is loaded. Since the program most likely doesn't know about the class until it is registered, +load would be more appropriate.

Andrea Over a year ago

so the solution is just overriding that method?

Joshua Weinberg Over a year ago

It really depends on exactly what register is supposed to be doing. I find the whole architecture described about to be...bad

Andrea Over a year ago

@JoshuaWeinberg what is your suggestion for my problem?I know it seems not a good practise but my solution builds code that doesnt need to be edited for new types of widgets

Joshua Weinberg Over a year ago

You don't describe enough for me to give you a valid alternative. But within what you said you're doing, implementing +load in the classes you want to register with the singleton should work.

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Dave DeLong · Accepted Answer · 2011-09-28 17:15:33Z

0

A way you could do it is with the runtime:

Grab a list of all the classes known to the runtime.
Iterate the list, and check to see if the class conforms to your widget protocol
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.

answered Sep 28, 2011 at 17:15

Dave DeLong

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