Objective-C and use of SEL/IMP
Another question of mine about optimizing Obje开发者_运维知识库ctive C programs inspired the following: does anyone have a short example using SEL and IMP when theMethod has two (or more) integers for input?
Here's a good tutorial for getting the current IMP (with an overview of IMPs). A very basic example of IMPs and SELs is:
- (void)methodWithInt:(int)firstInt andInt:(int)secondInt { NSLog(@"%d", firstInt + secondInt); }
SEL theSelector = @selector(methodWithInt:andInt:);
IMP theImplementation = [self methodForSelector:theSelector];
//note that if the method doesn't return void, you have to explicitly typecast the IMP, e.g. int(* foo)(id, SEL, int, int) = ...
You could then invoke the IMP like so:
theImplementation(self, theSelector, 3, 5);
There's usually no reason to need IMPs unless you're doing serious voodoo--is there something specific you want to do?
Now that I have this working thanks to eman, I can add yet another example:
SEL cardSelector=@selector(getRankOf:::::::);
IMP rankingMethod=[eval methodForSelector:cardSelector];
rankingMethod(eval, cardSelector, 0, 1, 2, 3, 4, 5, 6);
I don't need this for anything useful, I just needed to satisfy my curiosity! Thank you again.
Here is another possible alternative. This avoids the crash but stubbing doesn't work.
- (void)setUp
{
[super setUp];
[self addSelector@selector(firstName) toClass:[User class]];
[self addSelector@selector(lastName) toClass:[User class]];
}
- (void)addSelector:(SEL)selector toClass:(Class)class
{
NSString *uniqueName = [NSString stringWithFormat:@"%@-%@", NSStringFromClass(class), NSStringFromSelector(selector)];
SEL sel = sel_registerName([uniqueName UTF8String]);
IMP theImplementation = [class methodForSelector:sel];
class_addMethod(class, selector, theImplementation, "v@:@");
}
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