如何使用NSJSONSerialization

我有一个JSON字符串（来自PHP json_encode()，看起来像这样：

[{"id": "1", "name":"Aaa"}, {"id": "2", "name":"Bbb"}]

我想将其解析为iPhone应用程序的某种数据结构。我想对我来说最好的是拥有一个字典数组，因此数组中的第0个元素是带有键"id" => "1"和的字典"name" => "Aaa"。

我不明白如何NSJSONSerialization存储数据。到目前为止，这是我的代码：

NSError *e = nil;
NSDictionary *JSON = [NSJSONSerialization 
    JSONObjectWithData: data 
    options: NSJSONReadingMutableContainers 
    error: &e];

这只是我在另一个网站上看到的示例。我一直在尝试JSON通过打印出诸如此类的元素和事物的数量来读取对象，但是我一直在得到EXC_BAD_ACCESS。

如何使用NSJSONSerialization解析上面的JSON，并将其转换为我提到的数据结构？

您的根json对象不是字典而是数组：

[{"id": "1", "name":"Aaa"}, {"id": "2", "name":"Bbb"}]

这可能使您清楚地了解如何处理它：

NSError *e = nil;
NSArray *jsonArray = [NSJSONSerialization JSONObjectWithData: data options: NSJSONReadingMutableContainers error: &e];

if (!jsonArray) {
  NSLog(@"Error parsing JSON: %@", e);
} else {
   for(NSDictionary *item in jsonArray) {
      NSLog(@"Item: %@", item);
   }
}

这是我的代码，用于检查接收到的json是数组还是字典：

NSError *jsonError = nil;
id jsonObject = [NSJSONSerialization JSONObjectWithData:jsonData options:kNilOptions error:&jsonError];

if ([jsonObject isKindOfClass:[NSArray class]]) {
    NSLog(@"its an array!");
    NSArray *jsonArray = (NSArray *)jsonObject;
    NSLog(@"jsonArray - %@",jsonArray);
}
else {
    NSLog(@"its probably a dictionary");
    NSDictionary *jsonDictionary = (NSDictionary *)jsonObject;
    NSLog(@"jsonDictionary - %@",jsonDictionary);
}

我已经为options：kNilOptions和NSJSONReadingMutableContainers尝试过了，并且都可以正常工作。

显然，在if-else块中创建NSArray或NSDictionary指针的情况下，实际的代码无法采用这种方式。

这个对我有用。您的data对象可能是，nil并且如rckoenes所述，根对象应该是一个（可变的）数组。参见以下代码：

NSString *jsonString = @"[{\"id\": \"1\", \"name\":\"Aaa\"}, {\"id\": \"2\", \"name\":\"Bbb\"}]";
NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
NSError *e = nil;
NSMutableArray *json = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&e];
NSLog(@"%@", json);

（我必须使用反斜杠对JSON字符串中的引号进行转义。）

您的代码看起来不错，除了结果是一个NSArray，而不是NSDictionary，这是一个示例：

前两行仅使用JSON创建数据对象，与从网上读取数据对象相同。

NSString *jsonString = @"[{\"id\": \"1\", \"name\":\"Aaa\"}, {\"id\": \"2\", \"name\":\"Bbb\"}]";
NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];

NSError *e;
NSMutableArray *jsonList = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&e];
NSLog(@"jsonList: %@", jsonList);

NSLog内容（词典列表）：

jsonList: (
           {
               id = 1;
               name = Aaa;
           },
           {
               id = 2;
               name = Bbb;
           }
           )

[{"id": "1", "name":"Aaa"}, {"id": "2", "name":"Bbb"}]

在上面的JSON数据中，您正在显示我们有一个包含字典数的数组。

您需要使用以下代码进行解析：

NSError *e = nil;
NSArray *JSONarray = [NSJSONSerialization JSONObjectWithData: data options: NSJSONReadingMutableContainers error: &e];
        for(int i=0;i<[JSONarray count];i++)
        {
            NSLog(@"%@",[[JSONarray objectAtIndex:i]objectForKey:@"id"]);
             NSLog(@"%@",[[JSONarray objectAtIndex:i]objectForKey:@"name"]);
        }

快速3/3 +

   //Pass The response data & get the Array
    let jsonData = try JSONSerialization.jsonObject(with: data!, options: .allowFragments) as! [AnyObject]
    print(jsonData)
    // considering we are going to get array of dictionary from url

    for  item  in jsonData {
        let dictInfo = item as! [String:AnyObject]
        print(dictInfo["id"])
        print(dictInfo["name"])
    }

以下代码从网络服务器获取JSON对象，并将其解析为NSDictionary。我已经使用了openweathermap API，此示例返回一个简单的JSON响应。为了简单起见，此代码使用同步请求。

   NSString *urlString   = @"http://api.openweathermap.org/data/2.5/weather?q=London,uk"; // The Openweathermap JSON responder
   NSURL *url            = [[NSURL alloc]initWithString:urlString];
   NSURLRequest *request = [NSURLRequest requestWithURL:url];
   NSURLResponse *response;
   NSData *GETReply      = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
   NSDictionary *res     = [NSJSONSerialization JSONObjectWithData:GETReply options:NSJSONReadingMutableLeaves|| NSJSONReadingMutableContainers error:nil];
   Nslog(@"%@",res);

@rckoenes已经向您展示了如何从JSON字符串正确获取数据。

对于您提出的问题：EXC_BAD_ACCESS[自动]释放对象后，几乎总是在您尝试访问该对象时出现。这不是特定于JSON的反序列化，而是与获取对象有关，然后在对象发布后对其进行访问。它通过JSON发出的事实并不重要。

有很多页面描述了如何调试它-您想要使用Google（或SO）obj-c zombie objects，尤其是，NSZombieEnabled对于您确定僵尸对象的来源而言，这对您来说是无价的。（“僵尸”是您释放对象但保留指向该对象的指针并在以后尝试引用它时所称的对象。）

带有do / try / catch块的Xcode 7（Beta）上的Swift 2.0：

// MARK: NSURLConnectionDataDelegate

func connectionDidFinishLoading(connection:NSURLConnection) {
  do {
    if let response:NSDictionary = try NSJSONSerialization.JSONObjectWithData(receivedData, options:NSJSONReadingOptions.MutableContainers) as? Dictionary<String, AnyObject> {
      print(response)
    } else {
      print("Failed...")
    }
  } catch let serializationError as NSError {
    print(serializationError)
  }
}

注意：对于Swift 3。您的JSON字符串返回的是Array而不是Dictionary。请尝试以下方法：

        //Your JSON String to be parsed
        let jsonString = "[{\"id\": \"1\", \"name\":\"Aaa\"}, {\"id\": \"2\", \"name\":\"Bbb\"}]";

        //Converting Json String to NSData
        let data = jsonString.data(using: .utf8)

        do {

            //Parsing data & get the Array
            let jsonData = try JSONSerialization.jsonObject(with: data!, options: .allowFragments) as! [AnyObject]

            //Print the whole array object
            print(jsonData)

            //Get the first object of the Array
            let firstPerson = jsonData[0] as! [String:Any]

            //Looping the (key,value) of first object
            for (key, value) in firstPerson {
                //Print the (key,value)
                print("\(key) - \(value) ")
            }

        } catch let error as NSError {
            //Print the error
            print(error)
        }

#import "homeViewController.h"
#import "detailViewController.h"

@interface homeViewController ()

@end

@implementation homeViewController

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.tableView.frame = CGRectMake(0, 20, 320, 548);
    self.title=@"Jason Assignment";

    // Uncomment the following line to preserve selection between presentations.
    // self.clearsSelectionOnViewWillAppear = NO;

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;
    [self clientServerCommunication];
}

-(void)clientServerCommunication
{
    NSURL *url = [NSURL URLWithString:@"http://182.72.122.106/iphonetest/getTheData.php"];
    NSURLRequest *req = [NSURLRequest requestWithURL:url];
    NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:req delegate:self];
    if (connection)
    {
        webData = [[NSMutableData alloc]init];
    }
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [webData setLength:0];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [webData appendData:data];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSDictionary *responseDict = [NSJSONSerialization JSONObjectWithData:webData options:0 error:nil];

    /*Third party API
     NSString *respStr = [[NSString alloc]initWithData:webData encoding:NSUTF8StringEncoding];
     SBJsonParser *objSBJson = [[SBJsonParser alloc]init];
     NSDictionary *responseDict = [objSBJson objectWithString:respStr]; */
    resultArray = [[NSArray alloc]initWithArray:[responseDict valueForKey:@"result"]];
    NSLog(@"resultArray: %@",resultArray);
    [self.tableView reloadData];
}


- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
//#warning Potentially incomplete method implementation.
    // Return the number of sections.
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
//#warning Incomplete method implementation.
    // Return the number of rows in the section.
    return [resultArray count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
    }

    // Configure the cell...
    cell.textLabel.text = [[resultArray objectAtIndex:indexPath.row] valueForKey:@"name"];
    cell.detailTextLabel.text = [[resultArray objectAtIndex:indexPath.row] valueForKey:@"designation"];

    NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:[[resultArray objectAtIndex:indexPath.row] valueForKey:@"image"]]];
cell.imageview.image = [UIImage imageWithData:imageData];

    return cell;
}

/*
// Override to support conditional editing of the table view.
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the specified item to be editable.
    return YES;
}
*/

/*
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete the row from the data source
        [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }   
    else if (editingStyle == UITableViewCellEditingStyleInsert) {
        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
    }   
}
*/

/*
// Override to support rearranging the table view.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
}
*/

/*
// Override to support conditional rearranging of the table view.
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the item to be re-orderable.
    return YES;
}
*/


#pragma mark - Table view delegate

// In a xib-based application, navigation from a table can be handled in -tableView:didSelectRowAtIndexPath:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Navigation logic may go here, for example:
     //Create the next view controller.
    detailViewController *detailViewController1 = [[detailViewController alloc]initWithNibName:@"detailViewController" bundle:nil];

 //detailViewController *detailViewController = [[detailViewController alloc] initWithNibName:@"detailViewController" bundle:nil];

 // Pass the selected object to the new view controller.

 // Push the view controller.
 detailViewController1.nextDict = [[NSDictionary alloc]initWithDictionary:[resultArray objectAtIndex:indexPath.row]];
 [self.navigationController pushViewController:detailViewController1 animated:YES];

    // Pass the selected object to the new view controller.

    // Push the view controller.
  //  [self.navigationController pushViewController:detailViewController animated:YES];
}



@end

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    empName.text=[nextDict valueForKey:@"name"];
    deptlbl.text=[nextDict valueForKey:@"department"];
    designationLbl.text=[nextDict valueForKey:@"designation"];
    idLbl.text=[nextDict valueForKey:@"id"];
    salaryLbl.text=[nextDict valueForKey:@"salary"];
    NSString *ImageURL = [nextDict valueForKey:@"image"];
    NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:ImageURL]];
    image.image = [UIImage imageWithData:imageData];
}

问题似乎与对象的自动释放有关。NSJSONSerialization JSONObjectWithData显然正在创建一些自动释放的对象，并将其传递回给您。如果尝试将其应用到其他线程，则无法将其释放，因为无法在其他线程上将其释放。

技巧可能是尝试对该字典或数组进行可变复制并使用它。

NSError *e = nil;
id jsonObject = [NSJSONSerialization 
JSONObjectWithData: data 
options: NSJSONReadingMutableContainers 
error: &e] mutableCopy];

将NSDictionary视为NSArray不会导致Bad访问异常，但是当进行方法调用时可能会崩溃。

另外，可能选项在这里并不重要，但是最好给NSJSONReadingMutableContainers | NSJSONReadingMutableContainers | NSJSONReadingAllowFragments，但是即使它们是自动发布的对象，也可能无法解决此问题。

不好的例子，应该是这样的{{id“：1，” name“：” something as name“}

数字和字符串混合在一起。