如何检查一个元素是否在数组中

数组

let elements = [1, 2, 3, 4, 5, 5]

检查元素是否存在

elements.contains(5) // true

获取元素索引

elements.firstIndex(of: 5) // 4
elements.firstIndex(of: 10) // nil

获取元素数量

let results = elements.filter { element in element == 5 }
results.count // 2

如果有人想要查找一个indexPath是否在选中的列表中（例如在UICollectionView或UITableView的cellForItemAtIndexPath函数中），请注意以下内容：

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

var arrelemnts = ["sachin", "test", "test1", "test3"]

 if arrelemnts.contains("test"){
    print("found")   }else{
    print("not found")   }

这是我刚写的小扩展，用于检查我的委托数组是否包含委托对象 (适用于Swift 2)。 :) 它还可以很好地处理值类型。

extension Array
{
    func containsObject(object: Any) -> Bool
    {
        if let anObject: AnyObject = object as? AnyObject
        {
            for obj in self
            {
                if let anObj: AnyObject = obj as? AnyObject
                {
                    if anObj === anObject { return true }
                }
            }
        }
        return false
    }
}

extension Array {
     func contains<T>(_ object: T) -> Bool where T: Equatable {
         !self.filter {$0 as? T == object }.isEmpty
     }
 }

这可以用作：

if myArray.contains(myItem) {
   // code here
}

你觉得使用哈希表来完成这个任务怎么样？像这样：

首先，创建一个“哈希映射”通用函数，扩展序列协议。

extension Sequence where Element: Hashable {

    func hashMap() -> [Element: Int] {
        var dict: [Element: Int] = [:]
        for (i, value) in self.enumerated() {
            dict[value] = i
        }
        return dict
    }
}

只要数组中的项符合可哈希的要求，比如整数或字符串，这个扩展就可以工作。以下是用法...

let numbers = Array(0...50) 
let hashMappedNumbers = numbers.hashMap()

let numToDetect = 35

let indexOfnumToDetect = hashMappedNumbers[numToDetect] // returns the index of the item and if all the elements in the array are different, it will work to get the index of the object!

print(indexOfnumToDetect) // prints 35

但现在，让我们专注于检查元素是否在数组中。

let numExists = indexOfnumToDetect != nil // if the key does not exist 
means the number is not contained in the collection.

print(numExists) // prints true

Swift

如果您不使用对象，则可以使用此代码进行包含。

let elements = [ 10, 20, 30, 40, 50]

if elements.contains(50) {

   print("true")

}

var cliectScreenList = [ATModelLeadInfo]()
var cliectScreenSelectedObject: ATModelLeadInfo!

{ $0.user_id == cliectScreenSelectedObject.user_id }

{ "\($0.user_id)" == "\(cliectScreenSelectedObject.user_id)" }

if cliectScreenSelected.contains( { $0.user_id == cliectScreenSelectedObject.user_id } ) == false {

    cliectScreenSelected.append(cliectScreenSelectedObject)

    print("Object Added")

} else {

    print("Object already exists")

 }

Swift 4.2 +
通过下面的函数，您可以轻松验证您的实例是否为数组。

func verifyIsObjectOfAnArray<T>(_ object: T) -> Bool {
   if let _ = object as? [T] {
      return true
   }

   return false
}

func verifyIsObjectOfAnArray<T>(_ object: T) -> [T]? {
   if let array = object as? [T] {
      return array
   }

   return nil
}