将Int转换为Bool [英] Converting Int to Bool

问题描述

在Swift 2.x中我相信我能做到：

In Swift 2.x I believe I could do:

let number = 1
let result = Bool(number)

print(result) // prints out: true

但是自从Swift 3以来我一直无法做到这一点并且它给了我错误：

But since Swift 3 I've been unable to do this and it gives me the error:

无法调用类型'Bool'的初始化程序
类型的参数列表'（Int）'

Cannot invoke initialiser for type 'Bool' with an argument list of type '(Int)'

目前我正在使用扩展名来转换 Int 到 Bool 但是我想知道是否没有构建选项来执行此操作。

Currently I'm using an extension to convert an Int to a Bool but I was wondering if there isn't a build in option to do this.

推荐答案

不，从来没有明确的内置选项将 Int 转换为 Bool ，请参阅 <$ c的语言参考$ c> Bool 了解详情。

No, there is and has never been an explicit built in option for conversion of Int to Bool, see the language reference for Bool for details.

但是，仍然存在初始化程序 NSNumber 。区别在于Swift数字类型与 NSNumber 之间的隐式桥接已在Swift 3中删除（之前允许显式为 Bool by Int 初始化）。您仍然可以通过显式执行从 Int 到 NSNumber <的转换，通过 NSNumber 初始化程序访问它/ code>：

There exists, still, however, an initializer by NSNumber. The difference is that implicit bridging between Swift numeric type and NSNumber has been removed in Swift 3 (which previously allowed what seemed to be explicit Bool by Int initialization). You could still access this by NSNumber initializer by explicitly performing the conversion from Int to NSNumber:

let number = 1
let result = Bool(number as NSNumber)

print(result) // true

正如@Hamish在下面的评论中写道：如果我们离开初始化器的主题并只关注最终结果（实例化 Bool 实例给定 Int 实例）我们可以简单地使用！= 运算符来获取 Int 值（具体来说，带签名的运算符） func！=（lhs：Int，rhs：Int） - > Bool ），使用轻松实现的概括！= 算子方法：

As @Hamish writes in his comment below: if we leave the subject of initializers and just focus on the end result (instantiating a Bool instance given the value of an Int instance) we can simply make use of the != operator for Int values (specifically, the operator with signature func !=(lhs: Int, rhs: Int) -> Bool), a generalization easily achievable using the != operator approach:

let number = -1
let result = number != 0

print(result) // true

---

很像你自己以及 @ JAL在他的答案中描述，您可以通过 Int 构建自己的 Bool 初始化程序，但您也可以考虑对符合 整数的任何类型进行概括。 协议：

---

Much like you yourself as well as @JAL describes in his answer, you could construct your own Bool by Int initializer, but you might as well consider generalizing this for any type conforming to the Integer protocol:

extension Bool {
    init<T: Integer>(_ num: T) {
        self.init(num != 0)
    }
}

/* example usage */
let num1: Int8 = -1
let num2: Int = 3
let num3: UInt64 = 0
// ....
let result1 = Bool(num1) // true
let result2 = Bool(num2) // true
let result3 = Bool(num3) // false

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