注意事项

1. @escaping 无法加在可选参数前面

只有在函数参数位置的闭包才是默认非逃逸的。包括可选(Optional)参数在内都是默认逃逸的。

Basically, @escaping is valid only on closures in function parameter position. The noescape-by-default rule only applies to these closures at function parameter position, otherwise they are escaping. Aggregates, such as enums with associated values (e.g. Optional), tuples, structs, etc., if they have closures, follow the default rules for closures that are not at function parameter position, i.e. they are escaping.

2. foreach里不可以使用break, continue

3. layoutIfNeeded 要用rootView调用 通常就是self.view.layoutIfNeeded。 用某个加载在上面的subView调用不会有动画。