Objective-C Method Swizzling

swizzling.m

// source: https://www.mikeash.com/pyblog/friday-qa-2010-01-29-method-replacement-for-fun-and-profit.html

#import <objc/runtime.h>

void __attribute__((weak)) MethodSwizzle(Class c, SEL origSEL, SEL overrideSEL) {
    Method origMethod = class_getInstanceMethod(c, origSEL);
    Method overrideMethod = class_getInstanceMethod(c, overrideSEL);
    if (class_addMethod(c, origSEL, method_getImplementation(overrideMethod), method_getTypeEncoding(overrideMethod))) {
        class_replaceMethod(c, overrideSEL, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
    } else {
        method_exchangeImplementations(origMethod, overrideMethod);
    }
}