swift init 可选数组包装

Question

您好，我是 swift 的新手，我正在尝试创建一个可选的数组，有时它为空，我不知道正确的语法是什么，这是代码

public final class Content: ResponseObject,ResponseCollection {
public let created: String
public let name: String
public let children: [Content]?

@objc required public init?(response: NSHTTPURLResponse, representation: AnyObject) {
    self.name = representation.valueForKeyPath("name") as! String
    self.created = representation.valueForKeyPath("created") as! String       
    self.children = Content.collection(response:response, representation: representation.valueForKeyPath("children")!)
}

@objc public static func collection(#response: NSHTTPURLResponse, representation: AnyObject) -> [Content] {
    var contents: [Content] = []

    if let representation = representation as? [[String: AnyObject]] {
        for contentRepresentation in representation {
            if let content = Content(response: response, representation: contentRepresentation) {
                contents.append(content)
            }
        }
    }

    return contents
}

children 有时可以为 nil，但为 null 时会崩溃。

Answer 1

self.children = Content.collection(response:response, representation: representation.valueForKeyPath("children")!)

使用!，因为您正在强制进行可选解包。所以如果“子”路径不存在，应用程序将崩溃。

更新：

valueForKeyPath(_:) 的签名是：

func valueForKeyPath(_ keyPath: String) -> AnyObject?

返回一个可选的。我建议你这样做：

@objc required public init?(response: NSHTTPURLResponse, representation: AnyObject) {
    if let namePath = representation.valueForKeyPath("name") as? String, createdPath = representation.valueForKeyPath("created") as? String, childrenPath = representation.valueForKeyPath("children") as? String {
        self.name = namePath
        self.created = createdPath
        self.children = Content.collection(response:response, representation: childrenPath)
    }
    else {
        println("name path, created path, or children path does not exists")
    }
}

将 替换为正确的类类型。