如何檢查元素是否在數組中

本文翻譯自：How to check if an element is in an array

In Swift, how can I check if an element exists in an array? 在Swift中，如何檢查數組中是否存在元素？ Xcode does not have any suggestions for contain , include , or has , and a quick search through the book turned up nothing. Xcode沒有對contain ， include或has任何建議，並且快速搜索本書不會發現任何建議。 Any idea how to check for this? 知道如何檢查嗎？ I know that there is a method find that returns the index number, but is there a method that returns a boolean like ruby's #include? 我知道有find返回索引號的方法的方法，但是有沒有方法返回像ruby的#include?這樣的布爾值的方法#include? ? ？

Example of what I need: 我需要的示例：

var elements = [1,2,3,4,5]
if elements.contains(5) {
  //do something
}

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#1樓

參考：https://stackoom.com/question/1d82K/如何檢查元素是否在數組中

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#2樓

I used filter. 我用過濾器。

let results = elements.filter { el in el == 5 }
if results.count > 0 {
    // any matching items are in results
} else {
    // not found
}

If you want, you can compress that to 如果需要，可以將其壓縮爲

if elements.filter({ el in el == 5 }).count > 0 {
}

Hope that helps. 希望能有所幫助。

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Update for Swift 2 Swift 2更新

Hurray for default implementations! 歡呼使用默認實現！

if elements.contains(5) {
    // any matching items are in results
} else {
    // not found
}

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#3樓

Use this extension: 使用此擴展名：

extension Array {
    func contains<T where T : Equatable>(obj: T) -> Bool {
        return self.filter({$0 as? T == obj}).count > 0
    }
}

Use as: 用於：

array.contains(1)

Updated for Swift 2/3 已針對Swift 2/3更新

Note that as of Swift 3 (or even 2), the extension is no longer necessary as the global contains function has been made into a pair of extension method on Array , which allow you to do either of: 請注意，從Swift 3（甚至2）開始，不再需要擴展，因爲已將全局contains函數做成Array上的一對擴展方法，您可以執行以下任一操作：

let a = [ 1, 2, 3, 4 ]

a.contains(2)           // => true, only usable if Element : Equatable

a.contains { $0 < 1 }   // => false

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#4樓

Swift 2, 3, 4, 5: 斯威夫特2、3、4、5：

let elements = [1, 2, 3, 4, 5]
if elements.contains(5) {
    print("yes")
}

contains() is a protocol extension method of SequenceType (for sequences of Equatable elements) and not a global method as in earlier releases. contains()是SequenceType的協議擴展方法 （適用於Equatable元素的序列），而不是早期版本中的全局方法。

Remarks: 備註：

• This contains() method requires that the sequence elements adopt the Equatable protocol, compare eg Andrews's answer . 這個contains()方法要求序列元素採用Equatable協議，例如比較Andrews的answer 。
• If the sequence elements are instances of a NSObject subclass then you have to override isEqual: , see NSObject subclass in Swift: hash vs hashValue, isEqual vs == . 如果序列元素是NSObject子類的實例，則必須重寫isEqual: ：，請參見Swift中的NSObject子類：hash vs hashValue，isEqual vs == 。
• There is another – more general – contains() method which does not require the elements to be equatable and takes a predicate as an argument, see eg Shorthand to test if an object exists in an array for Swift? 還有另一個（更通用的） contains()方法不需要元素是相等的，並且需要謂詞作爲參數，請參見例如速記來測試對象是否存在於Swift數組中？ . 。

Swift older versions: Swift舊版本：

let elements = [1,2,3,4,5]
if contains(elements, 5) {
    println("yes")
}

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#5樓

Just in case anybody is trying to find if an indexPath is among the selected ones (like in a UICollectionView or UITableView cellForItemAtIndexPath functions): 以防萬一有人試圖查找indexPath是否在所選indexPath中（例如，在UICollectionView或UITableView cellForItemAtIndexPath函數中）：

    var isSelectedItem = false
    if let selectedIndexPaths = collectionView.indexPathsForSelectedItems() as? [NSIndexPath]{
        if contains(selectedIndexPaths, indexPath) {
            isSelectedItem = true
        }
    }

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#6樓

For those who came here looking for a find and remove an object from an array: 對於那些來這裏尋找並從數組中刪除對象的人：

Swift 1 斯威夫特1

if let index = find(itemList, item) {
    itemList.removeAtIndex(index)
}

Swift 2 迅捷2

if let index = itemList.indexOf(item) {
    itemList.removeAtIndex(index)
}

Swift 3, 4, 5 斯威夫特3，4，5

if let index = itemList.index(of: item) {
    itemList.remove(at: index)
}