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Accepted
fs_tigre
Asked: 2023-08-28 20:44:23 +0800 CST

在 Swift 中使用 contains(where:) 方法时如何访问满足特定条件的对象？

  • 772

我试图创建一个对象，如果它不存在于数组中，并删除一个重复的对象。以下代码可以成功确定对象是否已存在以及是否重复，我不确定的是如何捕获方法内 IF 语句内的实际对象，以便能够删除重复if existanceCount == 2{}对象contains(where:)之一。

如何捕获contains(where:)方法内的对象？

我基本上需要访问方法{$0}内部contains(where:)。

func dogCleanup(){
    var existanceCount = 0

    if dogs.contains(where: {$0.name == "Teddy"}){
        existanceCount += 1
        if existanceCount == 2{
            print("Dog exists 2 times, delete it")
            // how can I capture one of the duplicate objects
        }
    }else{
        print("Does NOT exist, add dog...")
    }
}

编辑：添加了dogNames数组。

func dogCleanup(){
    let dogNames = ["Teddy","Browny","Mia"]

    var existanceCount = 0
    for i in 0..<dogNames.count{
        if dogs.contains(where: {$0.name == dogNames[i]}){
            existanceCount += 1
            if existanceCount == 2{
                print("Dog exists 2 times, delete it")
                // how can I capture one of the duplicate objects
            }
        }else{
            print("Does NOT exist, add dog...")
        }
    }
}

编辑2。

这是我所期待的上下文。

实施例1

    let dogs = [Dog(name: "Teddy"), Dog(name: "Browny"),Dog(name: "Mia")] // objects in Core Data
    let dogNames = ["Teddy","Browny","Mia"] // default dog names

    func dogCleanup(){
        // do nothing, both match
    }
    // What I'm expecting after running the dogCleanup
    Teddy,Browny,Mia

实施例2

    let dogs = [Dog(name: "Teddy"), Dog(name: "Browny")] // objects in Core Data
    let dogNames = ["Teddy","Browny","Mia"]

    func dogCleanup(){
        // add Mia since it doesn't exist in Core Data
    }
    // What I'm expecting after running the dogCleanup
    Teddy, Browny, Mia

实施例3

    let dogs = [Dog(name: "Teddy"), Dog(name: "Browny"), Dog(name: "Browny")] // objects in Core Data
    let dogNames = ["Teddy","Browny","Mia"] // default dog names

    func dogCleanup(){
        // delete one Browny and add Mia since it doesn't exist in Core Data
    }
    // What I'm expecting after running the dogCleanup
    Teddy, Browny, Mia

实施例4

    let dogs = [Dog(name: "Teddy"), Dog(name: "Browny"), Dog(name: "Browny"), Dog(name: "Shadow")] // objects in Core Data
    let dogNames = ["Teddy","Browny","Mia"] // default dog names

    func dogCleanup(){
        // delete one Browny, add Mia and leave Shadow
    }
    // What I'm expecting after running the dogCleanup
    Teddy, Browny, Mia, Shadow
swift

1 个回答

  1. Best Answer

    实际上，如果您始终调用此方法来按名称选择一只狗并创建一只新狗（如果它不存在），则不必检查该对象是否多次出现。

    func getDog(by name: String) -> Dog {

    if let dog = dogs.first(where: {$0.name == name}){
        return dog
    } else {
        dogs.append(Dog(name: name))
    }
}
    • 1

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