Swift:循环遍历 Any 类型的集合？

Question

我是学习 swift 的新手，我遇到了这个问题，但似乎找不到答案。我创建了一个 Any 类型的集合，其中包括 Double、String、Int 和 Bool。当我尝试循环它时，出现错误:

"Value of protocol type 'Any' cannot conform to 'Sequence'.

这是练习:

"Create a collection of type [Any], including a few doubles, integers, strings, and booleans within the collection. Print the contents of the collection."

var items: Any = [5.2, "Hello", 2, true]
print(items)

"Loop through the collection. For each integer, print "The integer has a value of ", followed by the integer value. Repeat the steps for doubles, strings and booleans."

for item in items {
    if let unwrappedItem = item as? Int {
        print("The integer has a value of \(item)")
    } else if let unwrappedItem = item as? Double {
        print("The integer has a value of \(item)")
    }
}

预先感谢您的帮助!

Answer 1

您应该创建一个 [Any] 类型的对象，而不是 Any。然后您可以切换每个项目并将其转换为各自的类型:

let items: [Any] = [5.2, "Hello", 2, true, 2.7, "World", 10, false]

for item in items {
    switch item {
    case let item as Int: print("The integer has a value of \(item)")
    case let item as Double: print("The double has a value of \(item)")
    case let item as String: print("The string has a value of \(item)")
    case let item as Bool: print("The boolean has a value of \(item)")
    default: break
    }
}

---

这将打印

The double has a value of 5.2
The string has a value of Hello
The integer has a value of 2
The boolean has a value of true
The double has a value of 2.7
The string has a value of World
The integer has a value of 10
The boolean has a value of false

---

如果您需要单独迭代每种类型，您可以使用 case let 并将每个元素转换为所需的类型:

for case let item as Int in items {
    print("The integer has a value of \(item)")
}

for case let item as Double in items {
     print("The double has a value of \(item)")
}

for case let item as String in items {
    print("The string has a value of \(item)")
}

for case let item as Bool in items {
    print("The boolean has a value of \(item)")
}

---

这将打印

The integer has a value of 2
The integer has a value of 10
The double has a value of 5.2
The double has a value of 2.7
The string has a value of Hello
The string has a value of World
The boolean has a value of true
The boolean has a value of false

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