根据Cell内的内容，动态调整Cell高度，是常用的技术。在iOS 8 或者以上的版本内，这个技术不再需要自己计算行高，而是变得简单无比。

如下案例，假设一个Cell内有两个Label，其中一个单行，第二个多行，根据第二个Label的内容的不同，高度也会不同，这个高度的变大，会导致Cell跟着变高。

具体代码如下：

import UIKit    @UIApplicationMain    class AppDelegate: UIResponder, UIApplicationDelegate {        var window: UIWindow?        func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {            // Override point for customization after application launch.            window = UIWindow(frame: UIScreen.main.bounds)            window?.makeKeyAndVisible()            window?.rootViewController = Page()            return true        }    }    class Data: NSObject {        class func bookList() -> [Book] {            let bookList = [                Book(name: "1", details: "Short Text Short Text"),                Book(name: "2", details: "Long Text Long Text Long Text Long Text Long Text Long Text Long Text Long Text Long Text "),                ]            return bookList        }    }    class Page: UIViewController {        fileprivate let reuserId = "BookTableViewCellIdentifier"        fileprivate let bookList = Data.bookList()        fileprivate let tableview = UITableView()        override func viewDidLoad() {            super.viewDidLoad()            title = "Books"            configureTableView()        }        func configureTableView() {            tableview.dataSource = self            // key code 1             tableview.estimatedRowHeight = 100            // key code 2            tableview.rowHeight = UITableViewAutomaticDimension            tableview.register(Cell.self, forCellReuseIdentifier: reuserId)            view.addSubview(tableview)            tableview.frame = self.view.frame        }    }    extension Page : UITableViewDataSource {        func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {            return bookList.count        }        func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {            let cell = tableview.dequeueReusableCell(withIdentifier: reuserId, for: indexPath) as! Cell            let book = bookList[(indexPath as NSIndexPath).row]            cell.nameLabel.text = book.name            cell.detailLabel.text = book.details            return cell        }    }    class Cell: UITableViewCell {        let nameLabel = UILabel()        let detailLabel = UILabel()        override init(style: UITableViewCellStyle, reuseIdentifier: String?) {            super.init(style: style, reuseIdentifier: reuseIdentifier)            contentView.addSubview(nameLabel)            nameLabel.translatesAutoresizingMaskIntoConstraints = false            nameLabel.numberOfLines = 0            // key code 3            detailLabel.numberOfLines = 0            detailLabel.textColor = UIColor.lightGray            contentView.addSubview(detailLabel)            detailLabel.translatesAutoresizingMaskIntoConstraints = false            let view1 = detailLabel            let view2 = nameLabel            let views = ["view1":view1,"view2":view2]            let hConstraint1=NSLayoutConstraint.constraints(withVisualFormat: "H:|-[view1]-|", options: NSLayoutFormatOptions(rawValue: 0), metrics: nil, views: views)            self.contentView.addConstraints(hConstraint1)            let hConstraint2=NSLayoutConstraint.constraints(withVisualFormat: "H:|-[view2]-|", options: NSLayoutFormatOptions(rawValue: 0), metrics: nil, views: views)            self.contentView.addConstraints(hConstraint2)            let vConstraint=NSLayoutConstraint.constraints(withVisualFormat: "V:|-[view2]-5-[view1]-|", options: NSLayoutFormatOptions(rawValue: 0), metrics: nil, views: views)            self.contentView.addConstraints(vConstraint)        }        required init?(coder aDecoder: NSCoder) {            fatalError("init(coder:) has not been implemented")        }    }    class Book: NSObject {        let name: String        let details: String        init(name: String, details: String) {            self.name = name            self.details = details        }    }复制代码

此代码中，关键点有三个，分别标注在代码体内。

1. 设置估计行高和行高设置为UITableViewAutomaticDimension。此代码设置后，动态调整能力就会起作用。尽管名字和功能并不那么相符，但是确实就需要设置它才可以

   tableview.estimatedRowHeight = 100

   tableview.rowHeight = UITableViewAutomaticDimension

2. 设置第二个Label可以多行

   detailLabel.numberOfLines = 0

   这样，多余一行的内容才会扩展到下一行。这个高度的增加才能撑大Cell