UIViewController+Swizzled.m

//
//  UIViewController+Swizzled.m
//
//  Created by Rui Peres on 12/08/2013.
//  Copyright (c) 2013 Rui Peres. All rights reserved.
//

#import "UIViewController+Swizzled.h"
#import <objc/runtime.h>

@implementation UIViewController (Swizzled)

// Poor's man flag. Used to know if the methods are already Swizzed
static BOOL isSwizzed;

static NSString* logTag = @"";

+ (void)load
{
    isSwizzed = NO;
}

#pragma mark - Util methods

static void swizzInstance(Class class, SEL originalSelector, SEL swizzledSelector)
{
    Method originalMethod = class_getInstanceMethod(class, originalSelector);
    Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);

    BOOL didAddMethod = class_addMethod(class, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));

    if (didAddMethod) {
        class_replaceMethod(class, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
    }
    else {
        method_exchangeImplementations(originalMethod, swizzledMethod);
    }
}

- (void)logWithLevel:(NSUInteger)level
{
    NSString* paddingItems = @"";
    for (NSUInteger i = 0; i <= level; i++) {
        paddingItems = [paddingItems stringByAppendingFormat:@"--"];
    }

    NSLog(@"%@%@-> %@", logTag, paddingItems, [self.class description]);
}

#pragma mark - SwizzMethods

- (void)printPath
{
    if ([self parentViewController] == nil) {
        [self logWithLevel:0];
    }
    else if ([[self parentViewController] isMemberOfClass:[UINavigationController class]]) {
        UINavigationController* nav = (UINavigationController*)[self parentViewController];
        NSInteger integer = [[nav viewControllers] indexOfObject:self];
        [self logWithLevel:integer];
    }
    else if ([[self parentViewController] isMemberOfClass:[UITabBarController class]]) {
        [self logWithLevel:1];
    }
}

- (void)swizzviewDidAppear:(BOOL)animated
{
    [self printPath];

    // Call the original method (viewWillAppear)
    [self swizzviewDidAppear:animated];
}

#pragma mark - Public methods

+ (void)swizzIt
{
    // We won't do anything if it's already swizzed
    if (isSwizzed) {
        return;
    }

    swizzInstance([self class], @selector(viewDidAppear:), @selector(swizzviewDidAppear:));

    isSwizzed = YES;
}

+ (void)swizzItWithTag:(NSString*)tag
{
    logTag = tag;
    [self swizzIt];
}

+ (void)undoSwizz
{
    // We won't do anything if it has not been Swizzed
    if (!isSwizzed) {
        return;
    }

    isSwizzed = NO;
    swizzInstance([self class], @selector(swizzviewDidAppear:), @selector(viewDidAppear:));
}

@end