NSInvalidArgumentException'，原因：'-[__NSCFConstantString objectForKey:]：无法识别的选择器发送到实例 0x10256a1b0'

Posted 2023-03-11

【中文标题】NSInvalidArgumentException\'，原因：\'-[__NSCFConstantString objectForKey:]：无法识别的选择器发送到实例 0x10256a1b0\'

【英文标题】：NSInvalidArgumentException', reason: '-[__NSCFConstantString objectForKey:]: unrecognized selector sent to instance 0x10256a1b0'NSInvalidArgumentException'，原因：'-[__NSCFConstantString objectForKey:]：无法识别的选择器发送到实例 0x10256a1b0'

【发布时间】：2017-12-13 09:16:59

【问题描述】：

我有一个视图控制器，我在其中解析 xml 文件并在字典中获取其值，我试图获取标签中的值，但我的应用程序因显示此错误而崩溃*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFConstantString objectForKey:]: unrecognized selector sent to instance 0x10256a1b0'

我从字典中获取值的代码是这些，

 NSLog(@"string: %@", str);
NSDictionary *xmlDoc = [NSDictionary dictionaryWithXMLString:str];
NSLog(@"dictionary: %@", xmlDoc);

for (NSDictionary * oneCustomer in xmlDoc)

    // Create a new Customer record

    _lblID.text = [oneCustomer objectForKey:@"_id"];
    NSLog(@"Reg: %@ ",_lblID.text);

    _lblAlert.text = [oneCustomer objectForKey:@"_topic"];
    NSLog(@"Make: %@ ",_lblAlert.text);

    _lblxref.text = [oneCustomer objectForKey:@"xref"];

    NSLog(@"Type: %@ ",_lblxref.text);

    _lbltext.text = [oneCustomer objectForKey:@"text"];
    NSLog(@"Model: %@ ", _lbltext.text);

    _lblgraphic.text = [oneCustomer objectForKey:@"explanation"];
    NSLog(@"Model: %@ ",_lblgraphic.text);

    _lblprompt.text = [oneCustomer objectForKey:@"prompt"];
    NSLog(@"Model: %@ ",_lblprompt.text);

   _lblvoice.text = [oneCustomer objectForKey:@"_id"];
    NSLog(@"Model: %@ ", _lblvoice.text);

    //roils = [oneCustomer objectForKey:@"recommended oil"];
    //NSLog(@"Model: %@ ",roils);

如何消除此错误？ 这是我的字典，

dictionary: 
"__name" = QF;
"_category" = "C&M";
"_id" = AB2001;
"_ni_exempt" = no;
"_topic" = Alertness;
answers =     
    answer =         (
                    
            "_correct" = no;
            text = "give an arm signal as well as using your indicators";
        ,
                    
            "_correct" = no;
            text = "signal so that other drivers can slow down for you";
        ,
                    
            "_correct" = yes;
            text = "look over your shoulder for a final check";
        ,
                    
            "_correct" = no;
            text = "select a higher gear than normal";
        
    );
;
question =     
    explanation =         
        text = "If you want to make a U-turn, slow down and ensure that the road is clear in both directions. Make sure that the road is wide enough to carry out the manoeuvre safely.";
        voice =             
            "_id" = "AB2001-2";
        ;
    ;
    prompt = "Mark one answer";
    text = "Before you make a U-turn in the road, you should";
    voice =         
        "_id" = "AB2001-1";
    ;
    xref = "DES s4, DES s9, HC r159-161";
;

我必须从这本字典中提取所有值我怎样才能得到这个？

【问题讨论】：

显然在某些时候oneCustomer 是一个NSString 对象，而不是NSDictionary，所以你不能对它执行[oneCustomer objectForKey:someKey] 并导致崩溃。

那么现在该如何解决呢？如何从字典中获取值？ @Larme

这不是字典。你能给我们str的值吗？我有一些猜测，比如为什么 for 循环......所以 _lblID.text = [xmlDoc objectForKey:@"_id"]; 而不是 _lblID.text = [oneCustomer objectForKey:@"_id"];（等等），但这是疯狂的猜测......

我已经添加了字典，请检查它。@Larme

删除for (NSDictionary * oneCustomer in xmlDoc)，然后只做_lblID.text = [xmlDoc objectForKey:@"_id"];（等等，将oneCustomer替换为xmlDoc。

【参考方案1】：

希望对你有帮助，

-(void)fetchValuesFromDictioanry:(NSDictionary*)xmlDict

    for (NSString *string in [xmlDict allKeys])
    
        if ([[xmlDict valueForKey:string] isKindOfClass:[NSDictionary class]])
        
            [self fetchValuesFromDictioanry:[xmlDict valueForKey:string]];
        
        else if ([[xmlDict valueForKey:string] isKindOfClass:[NSString class]])
        

            if ([string isEqualToString:@"_id"] && [[xmlDict valueForKey:string] isKindOfClass:[NSString class]])
            
                _lblID.text = [xmlDict valueForKey:@"_id"];
            
            else
           
               NSLog(@"%@", NSStringFromClass([[xmlDict valueForKey:string] class]));
           
            NSLog(@"Model: %@ ", [xmlDict valueForKey:string]);

          //Set here other labels
        
        else if ([[xmlDict valueForKey:string] isKindOfClass:[NSArray class]])
        
            for (NSDictionary *dictionary in [xmlDict valueForKey:string]) 

                [self fetchValuesFromDictioanry:dictionary];
            
        
    

你可以这样调用，

[self fetchValuesFromDictioanry:xmlDoc];

【讨论】：

兄弟我已经解析了文件，问题是我得到的字典我想从中提取值。 @Hitesh Sultaniya

@Nabeel 当您将字典传递给此函数时，您将能够获取所需的所有值，对不起方法名称，但这只会遍历您的字典并在何时打印值key 的任何值都是字符串，你也不会得到任何错误

如何在视图加载时调用此方法？ @Hitesh Sultaniya

@Nabeel 请检查更新的答案，但参数应该是字典

兄弟，它只显示字典中的 id 和 topic 的值，而对于其他它显示为 null。 @Hitesh Sultaniya