arrays - Swift 4 按值复制内部有数组的对象数组

Question

我试图了解 copy() 如何函数在 Swift 4 中工作。我有两个类，其结构如下:

class Project {
    var id: Int
    var name: String
    var team: [Person]?

    init(id: Int, name: String, team: [Person]?) {
        self.id = id
        self.name = name
        self.team = team
    }
}

class Person {
    var id: Int
    var name: String
    var project: Project?

    init(id: Int, name: String, project: Project?) {
        self.id = id
        self.name = name
        self.project = project
    }
}

在我的程序中，我有一个项目数组，我想做的是通过以下方式创建数组中值的副本:

// arrProjects is some array of projects.
let projectsCopy = arrProjects.map { $0.copy() } as! [Project]

为了实现这一点，我实现了 NSCopying通过以下方式对两个类进行协议(protocol):

extension Project: NSCopying {
    public func copy(with zone: NSZone? = nil) -> Any {
        let teamCopy = self.team?.map { $0.copy() } as! [Person]?
        return Project(id: self.id, name: self.name, team: teamCopy)
    }
}

extension Person: NSCopying {
    public func copy(with zone: NSZone? = nil) -> Any {
        let projectCopy = self.project?.copy() as! Project?
        return Person(id: self.id, name: self.name, project: projectCopy)
    }
}

但是，当我运行代码时 arrProjects.map { $0.copy() }运行时，应用程序会卡住，就像在循环一样，并且显示 Thread 1: EXC_BAD_ACCESS (code=2, address=0x7ffee5a61ff8) let teamCopy = self.team?.map { $0.copy() } as! [Person]? 处抛出错误线。

知道我哪里出错了吗？

Answer 1

您不应该在 public func copy(with zone: NSZone? = nil) -> Any { 的定义中使用 copy() 您正在创建一个无限循环。

extension Project: NSCopying {
    public func copy(with zone: NSZone? = nil) -> Any {
        let copy = Project(id: self.id, name: self.name, team: self.team)
        return copy
    }
}

extension Person: NSCopying {
    public func copy(with zone: NSZone? = nil) -> Any {
        let copy = Person(id: self.id, name: self.name, project: self.project)
        return copy
    }
}