A Quick Way Of Knowing Which View Controller You Are Pushing Into

NavInjection.m

//A Quick Way Of Knowing Which View Controller You Are Pushing Into
//I find it extremely useful when debugging other team members' (unfamiliar) code
//Usage: Drop the snippet into a blank .m file. It'll NSLog when you are pushing a view controller.
#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#import <objc/message.h>

typedef void(^Block_IMP_pushViewController_animated)(__unsafe_unretained id _self, __unsafe_unretained id arg1, BOOL arg2);

static BOOL replaceMethodWithBlock(Class c, SEL origSEL, SEL newSEL, id block) {
    if ([c instancesRespondToSelector:newSEL]) {
        return YES;
    }
    Method origMethod = class_getInstanceMethod(c, origSEL);
    IMP impl = imp_implementationWithBlock(block);
    if (!class_addMethod(c, newSEL, impl, method_getTypeEncoding(origMethod))) {
        return NO;
    }else {
        Method newMethod = class_getInstanceMethod(c, newSEL);
        if (class_addMethod(c, origSEL, method_getImplementation(newMethod), method_getTypeEncoding(origMethod))) {
            class_replaceMethod(c, newSEL, method_getImplementation(origMethod), method_getTypeEncoding(newMethod));
        }else {
            method_exchangeImplementations(origMethod, newMethod);
        }
    }
    return YES;
}

static Block_IMP_pushViewController_animated helper(SEL targetSelector) {
    return [^(__unsafe_unretained id _self, __unsafe_unretained id arg1, BOOL arg2) {
        ((void ( *)(id, SEL, id, BOOL))objc_msgSend)(_self, targetSelector, arg1, arg2);
        NSLog(@"Push VC to  : %@", arg1);
    } copy];
}

static void swizzle() {
    SEL selector = @selector(pushViewController:animated:);
    NSString *selStr = NSStringFromSelector(selector);
    SEL newSelector = NSSelectorFromString([NSString stringWithFormat:@"%@%@", @"diwu_", selStr]);
    replaceMethodWithBlock([UINavigationController class], selector, newSelector, helper(newSelector));
}

__attribute__((constructor)) static void DWUTransition(void) {
    @autoreleasepool {
        swizzle();
    }
}