Swift 笔记 Array

字符串和数组转换

 func aryChangeStr() {
        let ary = ["1","3","4","hello","word"]
        let aryStr = ary.joined()
        print("数组转字符:\(aryStr)")//134helloword
        let aryStr2 = ary.joined(separator: "-")
        print("数组转字符以-分割:\(aryStr2)")//1-3-4-hello-word
    }
    
    func strChangeAry() {
        let str = "helloSwift"
        let strAry = Array(str)
        let strAry2 = str.compactMap { (item) -> String? in
            return "\(item)"
        }
        print("字符串转数组1:\(strAry)数组2:\(strAry2)")
        //["h", "e", "l", "l", "o", "S", "w", "i", "f", "t"]
        //["h", "e", "l", "l", "o", "S", "w", "i", "f", "t"]
        
        let str1 = "足球,,篮 球,乒乓球, 羽毛球, ,"
        let strAry3 = str1.split(separator: ",")
        let strAry4 = str1.components(separatedBy: ",")
        print("字符串转数组有分割字符,1:\(strAry3)数组2:\(strAry4)")
        //1,["足球", "篮 球", "乒乓球", " 羽毛球", " "]
        //2,["足球", "", "篮 球", "乒乓球", " 羽毛球", " ", ""]
        //在使用分隔符来分割字符串时，方法一与方法二的区别在于，
        //如果存在两个相邻的分隔符，
        //方法二会留存空字符串，方法一则会去掉空字符串。
    }

//MARK: 遍历数组

  func aryEach() {
       let ary = ["晴天","阴天","大雨","多云","大风","雨夹雪","小雨"]
       ary.forEach { (item) in
           print("数组遍历forEach:\(item)")
       }
       //for item in 比forEach省时
       for item in ary {
           print("数组遍历for item in :\(item)")
       }
       /// 该循环方式可设置开闭区间，设置时需注意数组越界
       for idx in 0..<ary.count {
           print("数组遍历for index in :\(ary[idx])")

       }
       for (idx,item) in ary.enumerated() {
           print("数组遍历for index item in ary.enumerated- index:\(idx)-item:\(item)")
       }
       
       var ary2: [Any?] = ary
       ary2.append(nil);
       ary2.insert(nil, at: 1)
       ary2.insert("swift", at: 1)
//        ary2.compactMap{return $0}
       print("数组ary2:\(ary2)")
//[Optional("晴天"), Optional("swift"), nil, Optional("阴天"), Optional("大雨"),
//Optional("多云"), Optional("大风"), Optional("雨夹雪"), Optional("小雨"), nil]
       let filterAry2 = ary2.compactMap { (item) in
           return item
       }
       //类型转换  ary2.compactMap{return "\($0)"}
       // ary2.compactMap { (item) -> String? in
       // return "\(item)"
       //   }
       print("过滤掉nil后的Ary2:\(filterAry2)")

       let filterAry3: [Any] = ary2.compactMap { (item) in
           let itemStr: String = item as? String ?? ""
           if itemStr.contains("雨"){
               return item
           }
           return nil
       }
       print("过滤到不包含雨的:\(filterAry3)")//["大雨", "雨夹雪", "小雨"]
         let filterAry4 = ary2.filter { (item) -> Bool in
           let itemStr: String = item as? String ?? ""
           return itemStr.contains("雨")
       }
       print("过滤到不包含雨的:\(filterAry4)")
       //[Optional("大雨"), Optional("雨夹雪"), Optional("小雨")]
   }

数组查询

   func searchAry() {
        ////注意：该方法是从数组的第一个位置开始查找，当有符合条件的对象就输出，剩下的不会继续查找。
        if let text = ary.first(where: {$0.hasSuffix("雨")}) {
            print("查找末尾字符是“雨”的对象:\(text)")
//查找末尾字符是“雨”的对象:大雨
        }
        ////注意：该方法是从数组的最后一个位置开始查找，当有符合条件的对象就输出，剩下的不会继续查找。
        if let text = ary.last(where: {$0.hasSuffix("雨")}) {
            print("从最后一个位置查找末尾字符是“雨”的对象:\(text)")
//从最后一个位置查找末尾字符是“雨”的对象:小雨
        }
        //lastIndex
        if let text = ary.firstIndex(where: {$0.hasSuffix("雨")}) {
            print("查找末尾字符是“雨”的对象:\(text)")
//查找末尾字符是“雨”的对象:2
        }
        let contains = ary.contains(where: {$0 == "小"})
        print(#"数组中是否有"小"这对象"#+"\(contains)")
//数组中是否有"小"这对象false
    }