...
[someController performSelector:@selector(someMethod)];
...
- (void)someMethod
{
  //bla bla...
}

SEL selector = NSSelectorFromString(@"someMethod");
IMP imp = [_controller methodForSelector:selector];
void (*func)(id, SEL) = (void *)imp;
func(_controller, selector);

SEL selector = NSSelectorFromString(@"processRegion:ofView:");
IMP imp = [_controller methodForSelector:selector];
CGRect (*func)(id, SEL, CGRect, UIView *) = (void *)imp;
CGRect result = func(_controller, selector, someRect, someView);

#pragma clang diagnostic push 
#pragma clang diagnostic ignored "-Warc-performSelector-leaks" 
   [someController performSelector: NSSelectorFromString(@"someMethod")]
#pragma clang diagnostic pop

#define SuppressPerformSelectorLeakWarning(Stuff) \
    do { \
        _Pragma("clang diagnostic push") \
        _Pragma("clang diagnostic ignored \"-Warc-performSelector-leaks\"") \
        Stuff; \
        _Pragma("clang diagnostic pop") \
    } while (0)

SuppressPerformSelectorLeakWarning(
    [_target performSelector:_action withObject:self]
);

id result;
SuppressPerformSelectorLeakWarning(
    result = [_target performSelector:_action withObject:self]
);

[self performSelector:aSelector withObject:nil afterDelay:0.0];