How do I formulate
[NSClassFromString(classname) myMethod:param1 more:param2];
such that the compiler does not give a warning saying that +myMethod may not be implemented ?
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4 Answers
[NSClassFromString(classname) performSelector: @selector(myMethod:more:) withObject:param1 withObject:param2];
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Quick & dirty: cast the return of NSClassFromString to id, if myMethod:more: is unique. The method binding doesn't happen until runtime, so the correct impl will be called.
Slightly cleaner: use NSObject's -(id)performSelector:(SEL)aSelector withObject:(id)anObject withObject:(id)anotherObject, if param1 and param2 are ids. It works for class methods too when called on a class object.
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Well, since you have multiple arguments, you can’t use -performSelector:withObject:. You’ll have to use what Objective-C uses under the hood, objc_msgSend(). But first you’ll have to cast it. Here’s how:
In your implementation file (.m), add the line #import <objc/message.h> to the top. Then, you need to cast objc_msgSend() appropriately. In this example, we’ll assume that param1 and param2 are Objective-C objects and that -myMethod:more: returns void.
void (*myMsgSend)(id self, SEL _cmd, id param1, id param2);
myMsgSend = (void(*)(id, SEL, id, id))objc_msgSend;
Once you’ve cast it appropriately, call your new function:
myMsgSend(obj, @selector(myMethod:more:), param1, param2);
1 Comment
bioffe
Do I understand it correctly, first line declares variable
myMsgSend which is pointer to a function with (id self, SEL _cmd, id param1, id param2) arguments ?Try typecasting the value returned by NSClassFromString() to id first.
