从对象数组中获取属性值数组

问题描述

有一个类叫做Employee.

class Employee {

    var id: Int
    var firstName: String
    var lastName: String
    var dateOfBirth: NSDate?

    init(id: Int, firstName: String, lastName: String) {
        self.id = id
        self.firstName = firstName
        self.lastName = lastName
    }
}

而且我有一组 Employee 对象.我现在需要的是将该数组中所有对象的 id 提取到一个新数组中.

And I have an array of Employee objects. What I now need is to extract the ids of all those objects in that array into a new array.

我也发现了这个类似的问题.但是它在 Objective-C 中，所以它使用 valueForKeyPath 来完成这个.

I also found this similar question. But it's in Objective-C so it's using valueForKeyPath to accomplish this.

如何在 Swift 中执行此操作?

How can I do this in Swift?

推荐答案

您可以使用 map 方法，该方法将某种类型的数组转换为另一种类型的数组 - 在您的情况下，从 Employee 数组到 Int 数组:

You can use the map method, which transform an array of a certain type to an array of another type - in your case, from array of Employee to array of Int:

var array = [Employee]()
array.append(Employee(id: 4, firstName: "", lastName: ""))
array.append(Employee(id: 2, firstName: "", lastName: ""))

let ids = array.map { $0.id }

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