swift – 具有默认值的Nonfailable枚举初始值设定项

enum ErrorCode: Int {
    case NoErr = 0,Err1,Err2,LastErr,DefaultErr

    init(value: Int) {
        if (value > LastErr.rawValue) {
            self = .DefaultErr
        } else {
            self = ErrorCode(rawValue: value)!
        }
    }
}

let error: ErrorCode = .LastErr
let anotherError: ErrorCode = ErrorCode(value: 99)

这是另一种变化：

enum ErrorCode: Int {
    case NoErr = 0,LastErr

    init?(value: Int) {
        if (value > 3) {
            return nil
        } else {
            self = ErrorCode(rawValue: value)!
        }

    }
}

let error: ErrorCode = .LastErr
let anotherError: ErrorCode? = ErrorCode(value: 99)

这相当于：

enum ErrorCode: Int {
    case NoErr = 0,LastErr
}

let anotherError: ErrorCode? = ErrorCode(rawValue: 99)

因为Apple doc说明：

NOTE

The raw value initializer is a failable initializer,because not every
raw value will return an enumeration member. For more information,see
Failable Initializers.

但一般来说,如果你想使用带有rawvalue的枚举,你应该期望一个可选的,并将nil返回值视为枚举定义之外的默认错误情况.那是我的建议.