swift5（5）流程控制

感谢作者
https://www.jianshu.com/p/5fa0e1c00225

        // 
        // For-In循环
        let names = ["Anna", "Alex", "Brian", "Jack"];
        for name in names {
            print("Hello, \(name)!");
        }
        let airports51 = ["job": "将军", "age": "16", "name": "zhangfei"];
        for (key,value) in airports51 {
            print("\(key)");
            print("\(value)");
        }
        for index in 1...5 {
            print("\(index) times 5 is \(index * 5)");
        }
        // 符合Strideable协议的任何类型的值都可以使用此函数
        // 例如整数或浮点类型。
        // 不包含结束值
        for item in stride(from: 0, to: 60, by: 5) {
            print(item, separator: "", terminator: " ");
            //!< 0 5 10 15 20 25 30 35 40 45 50 55
        }
        for item in stride(from: 0, to: Double.pi * 2, by: .pi/2) {
             print(item, separator: "", terminator: " ")//!<0.0 1.5707963267948966 3.141592653589793 4.71238898038469
        }
        // 区别于by，可能会包含结束值
        for item in stride(from: 0, through: 60, by: 5) {
            print(item, separator: "", terminator: " ");
            //!< 0 5 10 15 20 25 30 35 40 45 50 55 60
        }
        for item in stride(from: 0, through: Double.pi * 2, by: .pi/2) {
            print(item, separator: "", terminator: " ");
            //!<0.0 1.5707963267948966 3.141592653589793 4.71238898038469 6.283185307179586
        }
        
        // While循环
        var adc = 10;
        var apc = 0;
        while apc < adc {
            apc += 1;
            //!< 必须要有终止的条件 若 apc < adc 恒成立则程序陷入死循环
            print("条件成立"); //10
        }
        
        adc = 10;
        apc = 0;
        repeat {
            apc += 1;
            print("条件成立"); //!< 10次
        } while apc < adc
        
        // if
        adc = 20;
        if adc <= 32 {
            print("adc <= 32");
        } else if adc >= 86 {
            print("adc >= 86");
        } else {
            print("32 <adc< 86");
        }
        
        // switch
        let someCharacter: Character = "z";
        switch someCharacter {
        case "a":
            print("The first letter of the alphabet");
        case "z":
            print("The last letter of the alphabet");
        default:
            print("Some other character");
        }
        
        let anotherCharacter: Character = "a";
        switch anotherCharacter {
        case "a", "A":
            print("The letter A");
        default:
            print("Not the letter A");
        }
        
        // Range匹配
        adc = 20;
        apc = 0;
        var result = "";
        switch adc {
        case 0...10:
            result = "0...10";
        case 11..<20:
            result = "11..<20";
        case 20...30:
            result = "20...30";
        default:
            result = "beyond of range";
        }
        print(result);//!< 20...30
        
        // 元组
        let tuples : (Int,String,Int) = (404,"not found",-1);
        switch tuples {
        case (300,"精准匹配1",0):
            print("精准匹配1");
        case (0...200,"范围匹配1",-2...10):
            print("范围匹配1");
        case (_,_,-2...2):
            print("通配符匹配元组前两个,范围匹配最后一项");
        default:
            print("没有匹配到");
        }
        // 值绑定
        let anotherPoint = (2, 0);
        switch anotherPoint {
        case (let xx, 0):
            print("横坐标\(xx)");
        case (0, let yy):
            print("纵坐标 \(yy)");
        case let (xx, yy):
            print("任何点 (\(xx), \(yy))");
        }
        // Where
        let yetAnotherPoint = (1, -1);
        switch yetAnotherPoint {
        case let (x, y) where x==y:
            print("匹配到x与y相同的情况");
        case let(x,y) where x == -y:
            print("匹配到x与y为相反数的情况");
            //!<匹配到x与y为相反数的情况
        default:
            print("没有匹配的结果");
        }
        // 复合使用
        let someCharater = "e";
        switch someCharater {
        case "a","o","e","f":
            print("事例1，匹配成功");//!< log
        case "b","v","r","h":
            print("事例2，匹配成功");
        default:
            print("未匹配");
        }
        //复合事例中的值绑定，绑定的值类型必须匹配。case (let x, let y), (0, let x)这种是不被允许的 因为方法体中使用x，y时，若匹配的是 (0, let x)则y 无效。因为相同的值绑定应该存在于所有`case`之后的模式中。
        let stillAnotherPoint = (9, 0);
        switch stillAnotherPoint {
        case (let x, 0), (0, let x):
            //!< 'x' must be bound in every pattern:'x'必须绑定在每个模式中
            print("匹配成功");
        default:
            print("未匹配");
        }
        
        // 控制转移语句
        // continue
        let puzzleInput = "great minds think alike";
        var puzzleOutput = "";
        let charactersToRemove: [Character] = ["a", "e", "i", "o", "u", " "];
        for character in puzzleInput {
            if charactersToRemove.contains(character) {
                continue;
            }
            puzzleOutput.append(character);
        }
        print(puzzleOutput);
        //!< break下跳出循环,立即开始下一次迭代，输出为：grtmndsthnklk
        
        // break
        for character in puzzleInput {
            if charactersToRemove.contains(character) {
                break;
            }
            puzzleOutput.append(character);
        }
        print(puzzleOutput);
        //!< break下跳出循环不在开始，输出为gr
        
        // 贯穿（Fallthrough）
        let describe = 5;
        var description = "";
        switch describe {
        case 2, 3, 5, 7, 11, 13, 17, 19:
            description += "I am";
            fallthrough;
        case 18:
            description += " bob";
            //!< case 去掉fallthrough 则输出I am bob
            fallthrough;
        default:
            description += " and you?";
        }
        print(description);
        //!< I am bob and you?
        
        // 标签语句
        result = "";
        adc = 30;
        forLabel : for item in 9...adc {
           switchLabel :switch item {
            case 0...10:
                result += " 0...10";
                break switchLabel; //!<swift中break是默认的
            case 11..<20: //!<  若是11..<20区间则跳出for循环，开始下次迭代
                continue forLabel;
            case 20://!< 若是20 则立即终止for循环
                result += " 终止for循环";
                break forLabel;
            default:
                result += "beyond of range";
            }
        }
        print(result);
        //!< 0...10 0...10 终止for循环
        
        // 提前退出（throw,return）
        // 与if语句一样，guard语句根据表达式的布尔值执行语句。
        // 使用guard语句要求条件必须为true才能执行guard语句之后的代码。
        // 与if语句不同，guard语句总是有一个else子句
        // 如果条件为false，则执行else子句中的代码。
        // guard的else子句不能向下贯穿，
        // 必须使用转移控制的语句return或throw才能退出作用域。
//        adc = 30;
//        //! guard方法体不能向下贯穿，
//        // 需要使用`return`或`throw`退出作用域
//        guard adc > 30 else {
//            print("条件不成立");
//            return; //!< 提前结束了
//        }
//        //throw退出作用域
//        guard adc > 30 else {
//            print("条件不成立");
//            throw HttpError.authError;
//        }
        
        // 检查API可用性
        if #available(iOS 10, macOS 10.12, *) {
            // Use iOS 10 APIs on iOS, and use macOS 10.12 APIs on macOS
        } else {
            // Fall back to earlier iOS and macOS APIs
        }