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我试图了解该copy()函数在 Swift 4 中是如何工作的。我有两个结构如下的类：

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]

为此，我NSCopying通过以下方式为这两个类实现了协议：

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，当我运行代码和arrProjects.map { $0.copy() }运行时，应用程序会冻结，就好像它正在循环一样，并且在该行Thread 1: EXC_BAD_ACCESS (code=2, address=0x7ffee5a61ff8)抛出错误。let teamCopy = self.team?.map { $0.copy() } as! [Person]?

知道我哪里出错了吗？

4

1 回答 1

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

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
    }
}
于 2019-01-10T04:28:52.933 回答