objective-c - 如何在 Swift 中编写 init 方法？

Question

我想用 Swift 编写一个 init 方法。这里我在 Objective-C 中初始化了一个 NSObject 类:

-(id)initWithNewsDictionary:(NSDictionary *)dictionary
{
    self = [super init];
    if (self) {
        self.title           = dictionary[@"title"];
        self.shortDescription = dictionary[@"description"];
        self.newsDescription = dictionary[@"content:encoded"];
        self.link            = dictionary[@"link"];
        self.pubDate         = [self getDate:dictionary[@"pubDate"]];

    }
    return self;
}

如何在 Swift 中编写此方法？

Answer 1

我想这可能是您类(class)的良好基础:

class MyClass {

    // you may need to set the proper types in accordance with your dictionarty's content
    var title: String?
    var shortDescription: String?
    var newsDescription: String?
    var link: NSURL?
    var pubDate: NSDate?

    //

    init () {
        // uncomment this line if your class has been inherited from any other class
        //super.init()
    }

    //

    convenience init(_ dictionary: Dictionary<String, AnyObject>) {
        self.init()

        title = dictionary["title"] as? NSString
        shortDescription = dictionary["shortDescription"] as? NSString
        newsDescription = dictionary["newsDescription"] as? NSString
        link = dictionary["link"] as? NSURL
        pubDate = self.getDate(dictionary["pubDate"])

    }

    //

    func getDate(object: AnyObject?) -> NSDate? {
        // parse the object as a date here and replace the next line for your wish...
        return object as? NSDate
    }

}

高级模式

我想避免在项目中复制粘贴键，所以我将可能的键放入例如像这样的 enum:

enum MyKeys : Int {
    case KeyTitle, KeyShortDescription, KeyNewsDescription, KeyLink, KeyPubDate
    func toKey() -> String! {
        switch self {
        case .KeyLink:
            return "title"
        case .KeyNewsDescription:
            return "newsDescription"
        case .KeyPubDate:
            return "pubDate"
        case .KeyShortDescription:
            return "shortDescription"
        case .KeyTitle:
            return "title"
        default:
            return ""
        }
    }
}

你可以改进你的 convenience init(...) 方法，例如这样，将来您可以避免在代码中输入任何错误的键:

convenience init(_ dictionary: Dictionary<String, AnyObject>) {
    self.init()

    title = dictionary[MyKeys.KeyTitle.toKey()] as? NSString
    shortDescription = dictionary[MyKeys.KeyShortDescription.toKey()] as? NSString
    newsDescription = dictionary[MyKeys.KeyNewsDescription.toKey()] as? NSString
    link = dictionary[MyKeys.KeyLink.toKey()] as? NSURL
    pubDate = self.getDate(dictionary[MyKeys.KeyPubDate.toKey()])

}

注意:这只是您如何做到这一点的原始想法，根本没有必要使用便利初始化器，但它看起来很明显，因为我对您的 final类一无所知 – 您只分享了一个方法。