ios - Swift Optional(3) 在展开时得到 nil

Question

我是新来的，我有一个非常奇怪的问题。该应用程序通过 JSON 从外部 PHP 文件加载数据，解包并将结果集保存在数组中。奇怪的是，当 Category 为 1 时一切正常，但是当它为 2 时 Optional 值例如可选 (5) 变为零。

代码如下:

var jsonElement: NSDictionary = NSDictionary()
    let users: NSMutableArray = NSMutableArray()

    for(var i = 0; i < jsonResult.count; i++)
    {


        jsonElement = jsonResult[i] as! NSDictionary
       // print(jsonResult)
        let user = UserModel();
        print((Int32(jsonElement["Category"]! as! String)))

        //the following insures none of the JsonElement values are nil through optional binding
        if((Int32(jsonElement["Category"]! as! String)) == 1){

        if let FID = Int32(jsonElement["FID"]! as! String),let Category = Int32(jsonElement["Category"]! as! String)
        ,let UID = Int32(jsonElement["UID"]! as! String),let Comment = jsonElement["Comment"]! as? String,let A1 = jsonElement["A1"]! as? String,let A2 = jsonElement["A2"]! as? String,let Question = jsonElement["Question"]! as? String, let CID = Int32(jsonElement["CID"]! as! String){
            print(Category)
            user.FID = FID;
            user.Category = Category;
            user.UID = UID
            user.Comment = Comment
            user.A1 = A1;
            user.A2 = A2;
            user.Question = Question;
            user.CID = CID;
        }





        users.addObject(user)
        //print(user)
        }
        if((Int32(jsonElement["Category"]! as! String)) == 2){

            print(Int32(jsonElement["FID"]! as! String))

            if let FID = Int32(jsonElement["FID"]! as! String),let Category = Int32(jsonElement["Category"]! as! String)
                ,let UID = Int32(jsonElement["UID"]! as! String),let Comment = jsonElement["Comment"]! as? String,let Img1ID = Int32(jsonElement["Img1ID"]! as! String),let Img2ID = Int32(jsonElement["Img2ID"]! as! String),let Question = jsonElement["Question"]! as? String, let CID = Int32(jsonElement["CID"]! as! String){
                    print(Category)
                    user.FID = FID;
                    user.Category = Category;
                    user.UID = UID
                    user.Comment = Comment
                    user.Img1ID = Img1ID;
                    user.Img2ID = Img2ID;
                    user.Question = Question;
                    user.CID = CID;
            }

            users.addObject(user)


        }

    }

    print(users);

这里是控制台打印的值:

Data downloaded Optional(1) 1 Optional(1) 1 Optional(1) 1 Optional(2) Optional(4) ( "FID: 1, Category: 1, A1: Ja, A2: Nein, UID: 1, Year: nil, Sex: nil, Points: nil, CID: 1, Comment: test", "FID: 2, Category: 1, A1: Ja, A2: Nein, UID: 1, Year: nil, Sex: nil, Points: nil, CID: 2, Comment: test", "FID: 3, Category: 1, A1: Ja, A2: Nein, UID: 1, Year: nil, Sex: nil, Points: nil, CID: 3, Comment: test", "FID: nil, Category: nil, A1: nil, A2: nil, UID: nil, Year: nil, Sex: nil, Points: nil, CID: nil, Comment: nil" )

如您所见，数组中的最后一个值都是 nil，但是当我显示整个 JsonResult 时，存在匹配的值。没有人知道发生了什么事吗？是否有更好的解包值解决方案？

我真的很想听听你们的意见!

这是 jsonResult:

(
{
    A1 = Ja;
    A2 = Nein;
    CID = 1;
    Category = 1;
    Comment = "test";
    FID = 1;
    Question = "test";
    UID = 1;
},
{
    A1 = Ja;
    A2 = Nein;
    CID = 2;
    Category = 1;
    Comment = "test";
    FID = 2;
    Question = "test";
    UID = 1;
},
    {
    A1 = Ja;
    A2 = Nein;
    CID = 3;
    Category = 1;
    Comment = "test";
    FID = 3;
    Question = "test";
    UID = 1;
},
{
    CID = 4;
    Category = 2;
    Comment = "test";
    FID = 4;
    Img1ID = 1;
    Img2ID = 2;
    UID = 1;
}

)

Answer 1

您在一个 if let 表达式中列出了所有可能的字段，只有当所有字段都为 not nil 时才为真。

在您的情况下，“let Question = jsonElement["Question"]!as?String”将因“Category = 2”而失败。所以 if let block 不会被执行。