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* [section-infos-api] Add ASSectionInfo.h * Create Processes.md * Update ASSectionInfo.h * Update ASSectionInfo.h * Add more changes/info * More stuff * More updates * Make it a protocol * Update things * Oops * Update Misc.m * Update Overview.md * Update ASCollectionSection.h * Update ASCollectionSection.h
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Overview
There is an established pattern where UICollectionViewLayout talks directly to the collection view's delegate to get additional layout info e.g. the size of a header in a given section.
This pattern is established by Apple's flow layout, and it is used by Pinterest and I'm sure others. It is dangerous when used with ASDK because we update asynchronously, so for instance if you delete a section from your data source, the layout won't find out until later and in the meantime it may ask the delegate about a section that doesn't exist!
The solution is to capture this kind of information from the data source immediately when a section is inserted, and make it available to the layout as we update the UICollectionView so that everyone is on the same page.
Enter: ASSectionUserInfo
Internally, we use a private object ASCollectionSection to represent one version of a section of items and supplementaries. If the user wants, they can provide us with an ASSectionUserInfo object to accompany the section, which will be read synchronously when the section is inserted.
Usage During Layout
The collection view will make these section infos available in the same way that finished nodes are currently available.
Sequence Diagram:
Creation When Inserting Sections
The section infos for any inserted/reloaded sections are queried synchronously, before the node blocks for their items. The top part of this diagram is the same as the current behavior but I think it's useful info =)