最近改一个BUG，遇到了一个使用AutoLayout让内容撑开UIScrollView的场景； 试了半天才搞定撑开和可以滚动，特此记录一下。

代码如下：

////  ViewController.swift//  ScrollViewAutoLayoutDemo////  Created by Crazy凡 on 2019/4/2.//  Copyright © 2019 kongkaikai. All rights reserved.//import UIKitimport SnapKitclass ViewController: UIViewController {    let scrollView = UIScrollView()    let testlabel = UILabel()    override func viewDidLoad() {        super.viewDidLoad()        // Do any additional setup after loading the view, typically from a nib.        view.addSubview(scrollView)        scrollView.addSubview(testlabel)        scrollView.snp.makeConstraints { (maker) in            maker.center.equalToSuperview()            maker.width.lessThanOrEqualTo(UIScreen.main.bounds.width - 60)            maker.height.lessThanOrEqualTo(UIScreen.main.bounds.height - 80).priority(.required)            // 保障UIScrollView可以被撑开，low 是为了避免约束冲突            maker.height.equalTo(testlabel.snp.height).priority(.low)        }        testlabel.numberOfLines = 0        testlabel.snp.makeConstraints { (maker) in            maker.top.left.bottom.right.equalToSuperview()            maker.width.equalToSuperview()            // 保障可以正确的计算contentSize            maker.height.greaterThanOrEqualToSuperview()        }        testlabel.text = "测试字符串，多写一些测试撑开效果"    }}复制代码