話不多說直接添代碼

//
//  MLSelectCityViewController.swift
//  zhongXiang_Swift
//
//  Created by 瑪麗 on 2018/3/12.
//  Copyright ? 2018年 瑪麗. All rights reserved.
//

import UIKit
import ObjectMapper
import RealmSwift

class MLSelectCityViewController: MLBaseViewController {
    
    func requestData() {
        
        MLHttpTool.getAllCityList(parameters: nil) { (response) in
            
            let modelArr = Mapper<MLCityModel>().mapArray(JSONObject: response)
            guard modelArr?.count != 0 else {
                return
            }
            
            for model in modelArr! {
                model.letter = self.getFirCharactor(str: model.name!)
            }
            
            self.dataArray.setArray(modelArr!)
            
            //首字母升序排列
            self.getAllCityMetter()
            
            self.tableView.reloadData()
        }
    }
    
    //獲得所有的key值并排序，并返回排好序的數(shù)組
    func getAllCityKey()->NSArray{
        let keys = metterDict.allKeys as NSArray
        return keys.sortedArray(using: #selector(NSNumber.compare(_:))) as NSArray
    }
    
    //首字母相同的放在一起
    func getAllCityMetter(){
        for cityInfo in self.dataArray {
            let info = cityInfo as! MLCityModel
            let s = metterDict[info.letter ?? ""]
            if s == nil {
                var letterArr: NSMutableArray
                letterArr = NSMutableArray()
                metterDict.setObject(letterArr, forKey: info.letter! as NSCopying)
                letterArr.add(info)
            }else{
                let m_letterArr = metterDict[info.letter ?? ""] as! NSMutableArray
                m_letterArr.add(info)
            }
        }
    }
    
    func getFirCharactor(str: String) -> String {
        
        let mString = NSMutableString(string: str)
        CFStringTransform(mString, nil, kCFStringTransformToLatin, false)
        CFStringTransform(mString, nil, kCFStringTransformStripDiacritics, false)
        let string = mString.capitalized
        return string.substring(to: string.index(string.startIndex, offsetBy: 1))
    }
    
}

extension MLSelectCityViewController: UITableViewDataSource, UITableViewDelegate
{
    func numberOfSections(in tableView: UITableView) -> Int {
        let keys = self.getAllCityKey()
        return keys.count
    }
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        let keys = self.getAllCityKey()
        let keyStr = keys[section]
        let values = metterDict.object(forKey: keyStr)
        return ((values as AnyObject).count)!
    }
    
    //索引代理
    func sectionIndexTitlesForTableView(tableView: UITableView) -> [String]? {
        let keys = self.getAllCityKey() as! [String]
        return keys
    }
    func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        let keys = self.getAllCityKey() as! [String]
        //判斷keys是否為空
        if keys.count > 0 {
            return keys[section]
        }else{
            return nil
        }
        
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
        let keys = self.getAllCityKey()//所有的key值
        let keyStr = keys[indexPath.section]//選擇的是哪一組
        let values = metterDict.object(forKey: keyStr) as! NSArray//獲取該組下面的所有行
        let info = values[indexPath.row] as! MLCityModel//獲取選中的行
        
        cell.textLabel?.text = info.name
        cell.textLabel?.font = UIFont.systemFont(ofSize: 14)
        
        return cell
    }
}