method swizzle

+ (void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Class class = [self class];
        SEL viewDidLoadOriginalSelector = @selector(viewDidLoad);
        SEL viewDidLoadswizzledSelector = @selector(set_webViewControllerViewDidLoad);
        Method viewDidLoadOriginalMethod = class_getInstanceMethod(class, viewDidLoadOriginalSelector);
        Method viewDidLoadSwizzledMethod = class_getInstanceMethod(class, viewDidLoadswizzledSelector);
        BOOL didAddMethod = class_addMethod(class, viewDidLoadOriginalSelector,
                                            method_getImplementation(viewDidLoadSwizzledMethod),
                                            method_getTypeEncoding(viewDidLoadSwizzledMethod));
        if (didAddMethod) {
            class_replaceMethod(class, viewDidLoadswizzledSelector,
                                method_getImplementation(viewDidLoadOriginalMethod),
                                method_getTypeEncoding(viewDidLoadOriginalMethod));
        } else {
            method_exchangeImplementations(viewDidLoadOriginalMethod, viewDidLoadSwizzledMethod);
        }
    });