swift - 是否可以在Swift中编写失败的字符串编写器？

如果我有这个密码：

let a : Int? = 10;
let b : String? = "Apples";
let result = "We have \(a) of \(b)";
// result will be "We have Optional(10) of Optional(Apples)"

我可以通过添加默认值删除选项：

let result = "We have \(a ?? 0) of \(b ?? "")";
// result will be "We have 10 of Apples"

但是如果我想要，如果字符串中的任何选项都是nil，那么字符串的结果是nil呢？

let a : Int? = nil;
let b : String? = "Apples";
let result = "We have \(a) of \(b)";
// result will be nil

所以我可以这样写：

let a : Int? = nil;
let b : String? = "Apples";
if let result = "We have \(a) of \(b)" { self.process(result); }

编辑：
我真正想要达到的是：

func process (_ s: String?) {
    guard let s = s else { return; }
    print (s);
}

let a : Int? = nil;
let b : String? = "Apples";
let result = "We have \(a) of \(b)";
self.process (result);

谢谢。

最佳答案

您可以使用map/flatMap方法：

let a : Int? = nil
let b : String? = "Apples"

let result = a.flatMap { a in b.map { b in
    "We have \(a) of \(b)"
} }

结果是（常数）Optional。如果String?或nil中的任何一个是a，则为b，否则为具有未包装值的字符串。