iOS 检索 Web 响应数据后如何从 JSON 中检索值

Posted 2023-03-15

【中文标题】iOS 检索 Web 响应数据后如何从 JSON 中检索值

【英文标题】：iOS How to retrieve value from JSON after retrieving web response data

【发布时间】：2015-12-30 03:59:17

【问题描述】：

我正在尝试发出 nsurl 请求并设法检索出 Web 响应数据。问题是我想从 JSON 列表中检索特定参数。 我要检索的参数是“id”并将其显示在标签中。

这是我用于建立连接的 viewDIDLoad：

- (void)viewDidLoad 
    [super viewDidLoad];
    // Do any additional setup after loading the view.


    feeds = [[NSMutableArray alloc] init];

     NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"https://coolsoft.mousy.com/v1/messi/reports"]];

    // Prepare the variables for the JSON response


    // Create a mutable copy of the immutable request and add more headers
    NSMutableURLRequest *mutableRequest = [request mutableCopy];

    [mutableRequest addValue:@"application/json" forHTTPHeaderField:@"request"];
    // Make synchronous request

    request = [mutableRequest copy];

    // Log the output to make sure our new headers are there
    NSLog(@"%@", request.allHTTPHeaderFields);




    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
    [connection start];

    if(connection)
    
        _webResponseData = [NSMutableData data] ;


    
    else
    
        NSLog(@"Connection is NULL");
    

他是我的connectionDidFinishLoading方法：

-(void)connectionDidFinishLoading:(NSURLConnection *)connection 

    NSLog(@"Received %lu Bytes", (unsigned long)[_webResponseData length]);
//    NSString *theXML = [[NSString alloc] initWithBytes:
//                        [_webResponseData mutableBytes] length:[_webResponseData length] encoding:NSUTF8StringEncoding];

    // convert to JSON
    NSError *myError = nil;
    NSDictionary *res = [NSJSONSerialization JSONObjectWithData:self.webResponseData options:NSJSONReadingMutableLeaves error:&myError];
    NSString *icon;
    // show all values
    for(id key in res) 

        id value = [res objectForKey:key];

        NSString *keyAsString = (NSString *)key;
        NSString *valueAsString = (NSString *)value;

        NSLog(@"key: %@", keyAsString);
        NSLog(@"value: %@", valueAsString);
    

    // extract specific value...
    NSArray *results = [res objectForKey:@"id"];

    for (NSDictionary *result in results) 
      icon   = [result objectForKey:@"id"];
        NSLog(@"icon: %@", icon);

    

    output.text = icon;


    output = [[UILabel alloc] initWithFrame:CGRectMake(10, 10, 200, 100)]; //adjust label size and position as needed
    output.font = [UIFont fontWithName:@"BradleyHandITCTT-Bold" size: 23.0];
    output.textColor = [UIColor whiteColor];
    output.textAlignment = NSTextAlignmentCenter;
    output.numberOfLines = 0; //note: I said number of lines need to be 2
    output.backgroundColor = [UIColor clearColor];
    output.adjustsFontSizeToFitWidth = YES;
    output.tag = 100;

这是我对 res 字典进行 NSLOG 时的输出：

(  date = "2014-08-28T00:00:00Z"; id = 300005; title = "July 2014 USAA Phishing Campaign Uses KeNiHaCk Exploit"; uri = "/v1/joker/reports/300005"; ,  date = "2014-12-16T20:46:29Z"; id = 300062; title = "Two-Year Chinese Spearphishing Campaign Largely Targeted Japanese Aerospace and Energy Industries"; uri = "/v1/joker/reports/300062"; ,

这是我的错误信息：

-[__NSCFArray objectForKey:]: unrecognized selector sent to instance 0x136713360
2015-12-30 11:58:17.692 FYP_ios_APP[817:323807] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFArray objectForKey:]: unrecognized selector sent to instance 0x136713360'

【问题讨论】：

这已经被问了一千次了，你必须把你的json转换成字典然后用key-value检索数据，问之前请先google一下

NSArray *results = [res objectForKey:@"id"];这是错误的。你得到的是字符串而不是数组。

JSON parsing using NSJSONSerialization in iOS的可能重复

【参考方案1】：

您的 JSON 响应是 "id":300005,"title":"pink","date":"2014-08-28T00:00:00Z","uri":"www.hipster.com/hip "

所以，你可以使用 lblName.text = [res valueForKey:@"id"];

【参考方案2】：

你的 json 解析没问题，它给你 JSON 到 NSDictionary 但是您需要在传递 NSDictionary 对象时进行一些小的更改，如下所示。

查看下面的代码，它可能会对您有所帮助

-(void)connectionDidFinishLoading:(NSURLConnection *)connection 
    //"id":300005, "title":"pink", "date":"2014-08-28T00:00:00Z", "uri":"www.hipster.com/hip"
    NSLog(@"Received %lu Bytes", (unsigned long)[_webResponseData length]);

    // convert to JSON
    NSError *myError = nil;
    NSDictionary *res = [NSJSONSerialization JSONObjectWithData:self.webResponseData options:NSJSONReadingMutableLeaves error:&myError];
    NSString *icon;

    // show all values
    for(id key in [res allKeys]) 
        NSLog(@"key: %@", key);
        NSLog(@"value: %@", [res objectForKey:key]);
    

    // extract specific value...
    icon = [res valueForKey:@"id"];
    NSLog(@"icon: %@", icon);

    output.text = icon;

    output = [[UILabel alloc] initWithFrame:CGRectMake(10, 10, 200, 100)]; //adjust label size and position as needed
    output.font = [UIFont fontWithName:@"BradleyHandITCTT-Bold" size: 23.0];
    output.textColor = [UIColor whiteColor];
    output.textAlignment = NSTextAlignmentCenter;
    output.numberOfLines = 0; //note: I said number of lines need to be 2
    output.backgroundColor = [UIColor clearColor];
    output.adjustsFontSizeToFitWidth = YES;
    output.tag = 100;

更新

// convert to JSON
NSError *myError = nil;
NSArray *res = [NSJSONSerialization JSONObjectWithData:self.webResponseData options:NSJSONReadingMutableLeaves error:&myError];

// show all values
for(NSDictionary *dic in res) 
    for(NSString *key in [dic allKeys]) 
        NSLog(@"key: %@", key);
        NSLog(@"value: %@", [dic objectForKey:key]);
    

【讨论】：

-[__NSCFArray allKeys]：无法识别的选择器发送到实例 0x13eecdea0 2015-12-30 13:46:33.679 FYP_IOS_APP[864:338722] *** 由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因: '-[__NSCFArray allKeys]: 无法识别的选择器发送到实例 0x13eecdea0'

当我注销 res 的响应时，它显示：( date = "2014-08-28T00:00:00Z"; id = 300005; title = "July 2014 USAA 网络钓鱼活动使用 KeNiHaCk Exploit"; uri = "/v1/joker/reports/300005"; , date = "2014-12-16T20:46:29Z"; id = 300062; title = "为期两年的中国鱼叉式钓鱼活动主要针对日本航空航天和能源工业"; uri = "/v1/joker/reports/300062"; ,

@zac 你调试过代码吗？ & 应用程序在循环开始时是否给出错误？因为这似乎是其他问题，或者您可能在回复中收到 NSArray 并将其解析为 NSDictionary

@zac 首先通过NSLog(@"%@",[res class]) 检查您的res 类类型，如果它是NSArray Type，然后使用NSArray *res insted NSDictionary *res 并相应地解析您的数据。