代码里有如下描述
There are 2 different types of callbacks (selectors):
- update selector: the ‘update’ selector will be called every frame. You can customize the priority.
- custom selector: A custom selector will be called every frame, or with a custom interval of time
The ‘custom selectors’ should be avoided when possible. It is faster, and consumes less memory to use the ‘update selector’
那么问题来了，为什么custom selector 的效率不高呢？