出现Assertion failure in -[***** layoutSublayersOfLayer:]

在自定义的view中使用了[self layoutIfNeeded]方法，在iOS89上都没有错误，但是在iOS7上出现了页面错乱，解决方案就是在自定义的view里面添加如下代码：

+ (void)load
{
    Method existing = class_getInstanceMethod(self, @selector(layoutSubviews));
    Method new = class_getInstanceMethod(self, @selector(_autolayout_replacementLayoutSubviews));
    
    method_exchangeImplementations(existing, new);
}

- (void)_autolayout_replacementLayoutSubviews
{
    [super layoutSubviews];
    [self _autolayout_replacementLayoutSubviews]; // not recursive due to method swizzling
    [super layoutSubviews];
}