分配数组中项的值会使条件绑定中的Bound值必须为Optional类型

I am getting a compile error saying

我收到编译错误说

Bound value in a conditional binding must be an Optional type

Below is a screenshot of the code

下面是代码的屏幕截图

4 个解决方案

#1

You can convert the value of array[index] to an Optional doing something like this:

您可以将array [index]的值转换为Optional,执行以下操作:

if let value = Int?(array[index]){
    result += value
}

That's if your array contains Ints. You could also use AnyObject?, but you'll get a warning from xcode.

如果你的数组包含Ints那就是。你也可以使用AnyObject ?,但是你会收到来自xcode的警告。

#2

The array should be declared as Optional type, take Int?[] as an example,

该数组应声明为Optional类型,以Int?[]为例,

let array:Int?[] = [nil, 2, 3]
let index = 0
let count = array.count

for index in 0..count {
    if let value = array[index] {
        println(value)
    } else {
        println("no value")
    }
}

#3

if the type of the value of array[index] is of optional, you could simple do like this:

如果array [index]的值的类型是可选的,你可以这么简单:

if let value = array[index]{
 result += value
}

#4

In this case the compiler is complaining because array isn't a collection of Optional (nil-able) types. If it truly doesn't need to be, you don't actually need that if, since everything inside the array is guaranteed to be the same type, and that if statement won't protect you from a out-of-bounds error anyway. So just go with:

在这种情况下,编译器抱怨,因为array不是Optional(nil-able)类型的集合。如果确实不需要,那么实际上并不需要,因为,因为数组中的所有内容都保证是相同的类型,并且if语句无法保护您免受越界错误的影响。所以请继续:

while ++index < length {
    result += array[index]
}

or perhaps better:

或者更好:

for value in array {
    result += value
}

or even better:

甚至更好:

result = array.reduce(0) { $0 + $1 }