Python "or"在 Swift 中等效？

Question

由于 Swift 的酷行为，我正在寻找 Swift 中的 或 等价物。

像这样:

variable = value or default

我编码了 mine :

func |<T>(a:T?, b:T) -> T {
    if let a = a {
        return a
    }
    return b
}

但我想知道 Swift 中是否已经存在任何默认实现？

编辑:感谢答案，我在 Swift 书中找到了引用资料:

Nil Coalescing Operator

The nil coalescing operator (a ?? b) unwraps an optional a if it contains a value, or returns a default value b if a is nil. The expression a is always of an optional type. The expression b must match the type that is stored inside a.

The nil coalescing operator is shorthand for the code below:

    a != nil ? a! : b

The code above uses the ternary conditional operator and forced unwrapping (a!) to access the value wrapped inside a when a is not nil, and to return b otherwise. The nil coalescing operator provides a more elegant way to encapsulate this conditional checking and unwrapping in a concise and readable form. (source)

Answer 1

使用??:

var optional:String?
var defaultValue:String = "VALUE"

var myString:String = optional ?? defaultValue

print(myString)