约束&背后的iOS算法自动版面 [英] IOS algorithm behind constraint & Auto Layout

问题描述

我正在尝试对IOS中的layoutSubviews函数进行逆向工程，在该函数中它会计算自动调整大小和约束.通常，如果我们按顺序创建约束:A依赖于(受约束的)B，B依赖于C，并且C是使用固定框架初始化的，那么系统应该足够聪明才能按以下顺序实现计算:C-> B->避免不必要的循环.

i'm trying to reverse engineer the layoutSubviews function in IOS where it calculates the autosizes and contraints. Normally, if we create constraints in orders: A depends (constrained) B, B depends C, and C was inited with a fix frame, a system should need to be smart enough to realise the calculation in order: C -> B -> A to avoid unneeded loops.

我的问题是:IOS(或算法是什么)如何遍历NSLayoutContraint列表并按此顺序计算帧?

My question is: How does IOS (or what is the algorithm) traverse the list of NSLayoutContraint and calculate the frame in such order?

推荐答案

只是在有人需要时回答:IOS使用Cassowary工具包进行自动布局( http://www.cs.washington.edu/research/constraints/cassowary/)

Just answering in case anyone needs it: IOS use Cassowary toolkit to do auto layout (http://www.cs.washington.edu/research/constraints/cassowary/)

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