快速初始化可选数组包装

Question

Hi I'm new in swift I'm trying to have an Array that is optional, some times that is null, I don't know what is the proper syntax, here is the code

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 can be nil sometimes, but it crash when is null.

Answer 1

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

With the ! , because you are forcing optional unwrapping.. so if "children" path does not exist, the app will crash.

UPDATE:

The signature for valueForKeyPath(_:) is:

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

which returns an optional. I would suggest you to do:

@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")
    }
}

replace <"ClassType"> by the correct class type.