UIStackView - 想要一个百分比来定义每个项目

I want to put two views into a UIStackView. I want the top item to always be 30% of the space no matter what device (or orientation) that it appears. Thus, I want to have the bottom view to be 70%. How do I tell a UIStackView that I want to use a percentage?I want to put two views into a UIStackView. I w