[Swift通天遁地]二、表格表单-(2)创建右侧带有索引的UITableView(表单视图)

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目录：[Swift]通天遁地Swift

本文将演示如何给表格添加索引功能。

在项目导航区，打开视图控制器的代码文件【ViewController.swift】

现在开始编写代码，创建一个表格，并在表格右侧添加一列快捷索引。

import UIKit

//使当前的视图控制器类，遵循表格的数据源协议UITableViewDataSource
class ViewController: UIViewController, UITableViewDataSource {

    //创建一个字典对象，作为表格的数据来源。字典中的键，将作为表格的索引列表。
    var countries :Dictionary<String, [String]> = ["A": ["Afghanistan", "Albania", "Algeria", "Angola", "Australia", "Austria", "Azerbaijan"],
    "B":["Bangladesh","Belgium","Bhutan","Bolivia","Brazil","Bahrain","Bulgaria"], 
    "C":["Canada","Congo","Chile","China","Colombia","Cuba"], 
    "D":["Denmark","Djibouti","Dominica"],
    "E":["Egypt","Estonia","Ethiopia"], 
    "F":["Fiji","Finland","France"], 
    "G":["Gambia","Germany","Greece"],
    "H":["Haiti","Honduras","Hungary"], 
    "I":["India","Indonesia","Iran","Ireland","Iraq","Italy"], 
    "J":["Jordan","Japan"],
    "K":["Kazakhstan","Korea","Kuwait"], 
    "L":["Laos","Libya","Lebanon"], 
    "M":["Madagascar","Morocco","Malaysia","Mexico","Mali","Mozambique"],
    "N":["Nepal","Netherlands","Nigeria","New Zealand"],
    "O":["Oman"], 
    "P":["Pakistan","Panama","Philippines","Portugal"], 
    "Q":["Qatar"],
    "R":["Romania","South Africa","Russia"],
    "S":["Serbia & Montenegro","Senegal","Singapore","Somalia","Switzerland"],
    "T":["Thailand","Turkmenistan","Tunisia","Turkey"],
    "U":["United Arab Emirates","United States of America","Uzbekistan"], 
    "V":["Vanuatu","Venezuela","Vietnam"], 
    "Y":["Yemen"],
    "Z":["Zambia","Zimbabwe"]]
    
    //创建一个字符串数组，作为当前类的另一个属性
    var keys:[String] = []

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
        //将字典的键转换为数组，并执行升序排列，这个数组将被作为索引使用
        keys = Array(countries.keys).sorted()

        //获得设备的屏幕尺寸
        let screenRect = UIScreen.main.bounds
        //创建一个矩形区域，作为表格视图的显示区域。
        let tableRect = CGRect(x: 0,
                               y: 20, 
                                screenRect.size.width, 
                               height: screenRect.size.height - 20)
        //初始化一个指定显示区域的表格对象
        let tableView = UITableView(frame: tableRect)
        
        //设置表格对象的数据源为当前的视图控制器对象
        tableView.dataSource = self
        //并将表格视图添加到根视图中
        self.view.addSubview(tableView)
    }
    
    //添加一个代理方法，用来设置表格的段落的数量
    func numberOfSections(in tableView: UITableView) -> Int
    {
        //在此设置段落的数量，等于字典中键的数量
        return keys.count
    }
    
    //添加一个代理方法，用来设置表格的行数
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int
    {
        //获得当前段落的序号，
        let subCountries = countries[keys[section]]
        //然后获得在字典中，对应的值的数量
        //以该数量作为当前段落的行数
        return (subCountries?.count)!
    }
    
    //添加一个代理方法，用来设置表格的段落标题
    func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String?
    {
        return keys[section]
    }
    
    //添加一个代理方法，用来设置表格索引的标题数组
    func sectionIndexTitles(for tableView: UITableView) -> [String]?
    {
        return keys
    }
    
     //添加一个代理方法，用来初始化或复用表格中的单元格
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
    {
        //创建一个字符串常量，作为单元格的复用标识
        let identifier = "reusedCell"
        //根据复用标识，从表格中获得可以复用的单元格
        var cell = tableView.dequeueReusableCell(withIdentifier: identifier)
        
        //如果没有可以复用的单元格
        if(cell == nil)
        {
            //则初始化一个默认样式的单元格，并设置单元格的复用标识
            cell = UITableViewCell(style: UITableViewCellStyle.default, reuseIdentifier: identifier)
        }
        
        //根据当前单元格的段落序号，获得国家名称列表
        let subCountries = countries[keys[(indexPath as NSIndexPath).section]]
        //根据当前单元格的序号，获得该单元格需要显示的国家名称
        cell?.textLabel?.text = subCountries![(indexPath as NSIndexPath).row]
        
        //返回设置好的单元格
        return cell!
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}