以往对数组里元素按照首字母音序排序时并添加索引，我们可能会想到利用各种三方库，但较为麻烦。最近发现可以使用Apple提供的UILocalizedIndexedCollation进行本地化排序，本文主要完成两项任务：

• 完成本地JSON文件解析
• 利用UILocalizedIndexedCollation进行排序并添加sectionIndexTitles

先来看效果图：

效果图.gif

本文使用到的JSON文件部分内容如下

{
    "data": [
             {
             "countryName": "安道尔",
             "countryPinyin": "an dao er",
             "phoneCode": "376",
             "countryCode": "AD"
             },
             {
             "countryName": "阿拉伯联合酋长国",
             "countryPinyin": "a la bo lian he qiu zhang guo",
             "phoneCode": "971",
             "countryCode": "AE"
             }
           
}

我们将会根据countryName的首字母进行排序，但是首先我们得先完成本地JSON数据的解析，新建一个Country类，继承于NSObject:

import Foundation

typealias JSON = [String:Any]

class Country:NSObject {

   @objc var countryName:String!
    var countryPinyin :String!
    var phoneCode     :String!
    var countryCode   :String!

    init(dictionary: JSON) {
        self.countryName   = dictionary["countryName"] as! String
        self.countryPinyin = dictionary["countryPinyin"] as! String
        self.phoneCode     = dictionary["phoneCode"] as! String
        self.countryCode   = dictionary["countryCode"] as! String
    }
}

struct CountryFetcher {
    
    static func getCountries() -> [Country] {
        
        var countries = [Country]()
        
        if let filePath = Bundle.main.path(forResource: "Country", ofType: "json"){
            
            if  let jsonData = try? Data(contentsOf: URL(fileURLWithPath: filePath)){
                
                do{
                    let json = try JSONSerialization.jsonObject(with: jsonData, options:[]) as! JSON
                    
                    if  let dicts = json["data"] as? [JSON] {
                        countries = dicts.map({
                            return Country.init(dictionary: $0)
                        })
                    }
                    
                }catch let error as NSError{
                    print("解析出错: \(error.localizedDescription)")
                }
            }
            
        }
        return countries
    }
}

新建UILocalizedIndexedCollation Extension文件,创建排序方法：

extension UILocalizedIndexedCollation{
    
    func partitionObjects(array:[AnyObject], collationStringSelector:Selector) -> ([AnyObject], [String]) {
        var unsortedSections = [[AnyObject]]()
        
        //1. Create a array to hold the data for each section
        for _ in self.sectionTitles {
            unsortedSections.append([]) //appending an empty array
        }
        
        //2. Put each objects into a section
        for item in array {
            let index:Int = self.section(for: item, collationStringSelector:collationStringSelector)
            unsortedSections[index].append(item)
        }
        //3. sorting the array of each sections
        var sectionTitles = [String]()
        var sections = [AnyObject]()
        for index in 0 ..< unsortedSections.count { if unsortedSections[index].count > 0 {
            sectionTitles.append(self.sectionTitles[index])
            sections.append(self.sortedArray(from: unsortedSections[index], collationStringSelector: collationStringSelector) as AnyObject)
            }
        }
        return (sections, sectionTitles)
    }
}

新建CountryTableViewController,创建如下变量：

 var countries = [Country]() // country数组
 var countriesWithSections = [[Country]]() //每个section里是1个country数组，所有section里的country数组的集合
 var sectionTitles = [String]() // 标题数组，亦是索引文字数组
 let collation = UILocalizedIndexedCollation.current()

在ViewdidLoad方法里执行：

 countries = CountryFetcher.getCountries()
 let(countrArr, titlesArr) = collation.partitionObjects(array: countries,collationStringSelector: #selector(getter: Country.countryName)) 
 countriesWithSections = countryArr as![[Country]]
 sectionTitles = titlesArr

对tableView进行设置：

// 高度
 override func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        return 44
    }
    
    // titleForHeaderInSection
 override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        
        return sectionTitles[section]
    }
    
 override func numberOfSections(in tableView: UITableView) -> Int {
        return sectionTitles.count
    }
    
  override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return countriesWithSections[section].count
    }
    
 override func sectionIndexTitles(for tableView: UITableView) -> [String]? {
        return sectionTitles
    }
    
 override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        
        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
        let country = countriesWithSections[indexPath.section][indexPath.row]
        cell.textLabel?.text = country.countryName
        
        let phoneCodeLabel = UILabel(frame: CGRect(x: 0, y: 0, width: 80, height: 24))
        phoneCodeLabel.textAlignment = .right
        phoneCodeLabel.textColor = UIColor.lightGray
        phoneCodeLabel.font = UIFont.systemFont(ofSize: 15)
        phoneCodeLabel.text = "+" + country.phoneCode
        cell.accessoryView  = phoneCodeLabel
        return cell
    }

截止当前countryName都是中文字，假设部分countryName是英文，在中英文同时存在的情况下结果又如何呢？留给看此文的你去验证，将你的验证结果留在评论区。

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