Swift中的可選類型錯誤：致命錯誤：解開可選值時意外發現nil

Question

我正在嘗試使用FBSDK v4.x從Facebook獲得相冊。 我在下面使用此代碼，並在打印出結果后將結果作為json接收，但隨后會導致如下錯誤：' 致命錯誤：在此行代碼中意外發現nil，同時展開了可選值 '： let graphData = result .valueForKey（“ data”）一樣！ [FBSDKShareAPI] .so任何人都可以幫助我解決此錯誤。 提前致謝。

func fetchAlbum(){
    print(FBSDKAccessToken.currentAccessToken())
    let graphRequest: FBSDKGraphRequest = FBSDKGraphRequest(graphPath: "me?fields=albums", parameters: nil);
    graphRequest.startWithCompletionHandler({ (connection, result, error) -> Void in
        if let gotError = error{
            print(gotError.description);
        }
        else{
            print("fetched data: \(result)")
            if result != nil{ 
            let graphData = result.valueForKey("data") as! [FBSDKShareAPI]  
            var albums:[AlbumModel] =  [AlbumModel]();
            for obj:FBSDKShareAPI in graphData{
                let desc = obj.description;
                println(desc);
                let name = obj.valueForKey("name") as! String;
                println(name);
                if(name == "ETC"){
                    let test="";
                }
                let id = obj.valueForKey("id") as! String;
                var cover = "";
                if let existsCoverPhoto : AnyObject = obj.valueForKey("cover_photo"){
                    let coverLink = existsCoverPhoto as! String;
                    cover = "/\(coverLink)/photos";
                }
                //println(coverLink);
                let link = "/\(id)/photos";
                let model = AlbumModel(name: name, link: link, cover:cover);
                albums.append(model);
                }
            NSNotificationCenter.defaultCenter().postNotificationName("albumNotification", object: nil, userInfo: ["data":albums]);

            }
        }

    })
}

Answer 1

更好的是，你可以去

if let graphData = result?.valueForKey("data") as? [FBSDKShareAPI] {
    //bla
}

它應該為您做所有的零檢查

Answer 2

像這樣工作正常：

    func fetchAlbum(){
    print(FBSDKAccessToken.currentAccessToken())
    let graphRequest: FBSDKGraphRequest = FBSDKGraphRequest(graphPath: "me/albums", parameters: nil);
    graphRequest.startWithCompletionHandler({ (connection, result, error) -> Void in
        if let gotError = error{
            print(gotError.description);
        }
        else{
            let graphData: NSArray! = (result?["data"])! as? NSArray
            if (graphData != nil){

                var albums:[AlbumModel] =  [AlbumModel]();
                var obj: NSArray?
                for obj in graphData{
                let desc = obj.description;
                let name = obj.valueForKey("name") as! String;
                if(name == "ETC"){
                    let test="";
                }
                let id = obj.valueForKey("id") as! String;
                var cover = "";
                if let existsCoverPhoto : AnyObject = obj.valueForKey("cover_photo"){
                    let coverLink = existsCoverPhoto as! String;
                    cover = "/\(coverLink)/photos";
                }
                let link = "/\(id)/photos";
                let model = AlbumModel(name: name, link: link, cover:cover);
                albums.append(model);
                }
            NSNotificationCenter.defaultCenter().postNotificationName("albumNotification", object: nil, userInfo: ["data":albums]);

                }else{
                    print("--------------------------")
            }

        }

    })
}