Accurate contentSize

[ShenYj]

I'm not sure it is a bug, just wanna get some information for help.

The first time I use the IGListKit framework, I want to implement a CollectionView full of adaptive width fixed height items through IGListKit, and I hope to finally determine the height of the CollectionView according to the height of the content (of course, the content will not be too much, less than the screen height), and then I will get the contentSize of the collectionView after refreshing, However, it is not possible to get the correct height in the first place, and it is found that this height will change many times through KVO monitoring, and it will take some time to get the correct height in the end