无法使用类型为（String，Int）的索引对类型为[(String，Int)]的值进行下标操作 Swift 2

Question

无法使用类型为（String，Int）的索引对类型为[(String，Int)]的值进行下标操作 Swift 2

iosarraysswiftsortingtuples

4

我正在学习iOS开发，最近在尝试操作一个元组数组时遇到了问题。

我收到了以下错误消息：

“Cannot subscript a value of type '[(String, Int)]' with an index of type '(String, Int)'”

生成此错误的代码如下：

justStrings.append(filteredRestraunts[i2].0)

整个函数的作用如下：

    func filterBySliderValue () -> [String] {
    var filteredRestraunts: [(String, Int)]
    for var i = 0; i < restraunts.count; i++ {
        if restraunts[i].1 > Int(starSlider.value) {
            filteredRestraunts.append(restraunts[i])
        }
        else {filteredRestraunts.append(("", 1))}
    }
    var justStrings: [String]
    var i2 = 0
    for i2 in filteredRestraunts {
        justStrings.append(filteredRestraunts[i2].0)
    }
    return justStrings
}

这是餐厅数组：

var restraunts: [(String, Int)] = [("Dallas BBQ", 3), ("Chicken Express", 4), ("Starbucks", 5)]

谢谢你提前帮忙。

- Brandon Bradley

1个回答

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- Martin R · Accepted Answer

In

for i2 in filteredRestraunts {
    justStrings.append(filteredRestraunts[i2].0)
}

i2 不是索引，而是遍历数组 elements 的元素，即它是一个 (String, Int) 元组。你可能想要的是：

for i2 in filteredRestraunts {
    justStrings.append(i2.0)
}

额外说明：

The variable
```
var i2 = 0
```
is not used at all, i2 in the for-loop is a new variable whose scope is restricted to the loop.
The variables filteredRestraunts and justStrings are not initialized, so this should cause additional compiler errors.

Both loops can be replaced by a more functional approach using filter and map:

let filteredRestraunts = restraunts.filter { $0.1 > Int(starSlider.value) }
let justStrings = filteredRestraunts.map { $0.0 }

Which of course could be combined to

let justStrings = restraunts.filter { $0.1 > Int(starSlider.value) }.map { $0.0 }