How to use NSJSONSerialization

Question

I have a JSON string  from PHP s json encode   that looks like this      id    1    name   Aaa      id    2    name   Bbb      I want to parse this into some sort of data structure for my iPhone app  I guess the best thing for me would be to have an array of dictionaries  so the 0th element in the array is a dictionary with keys  id    gt   1  and  name    gt   Aaa     I do not understand how the NSJSONSerialization stores the data though  Here is my code so far   NSError  e   nil  NSDictionary  JSON    NSJSONSerialization      JSONObjectWithData  data      options  NSJSONReadingMutableContainers      error   amp e     This is just something I saw as an example on another website  I have been trying to get a read on the JSON object by printing out the number of elements and things like that  but I am always getting EXC BAD ACCESS   How do I use NSJSONSerialization to parse the JSON above  and turn it into the data structure I mentioned

User · Answer

Swift 2 0 on Xcode 7  Beta  with do try catch block      MARK  NSURLConnectionDataDelegate  func connectionDidFinishLoading connection NSURLConnection      do       if let response NSDictionary   try NSJSONSerialization JSONObjectWithData receivedData  options NSJSONReadingOptions MutableContainers  as  Dictionary lt String  AnyObject gt          print response        else         print  Failed                catch let serializationError as NSError       print serializationError

User · Answer

Your code seems fine except the result is an NSArray  not an NSDictionary  here is an example   The first two lines just creates a data object with the JSON  the same as you would get reading it from the net   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  amp e   NSLog   jsonList       jsonList     NSLog contents  a list of dictionaries    jsonList                                id   1                 name   Aaa                                            id   2                 name   Bbb

User · Answer

id    1    name   Aaa      id    2    name   Bbb      In above JSON data  you are showing that we have an array contaning the number of dictionaries   You need to use this code for parsing it   NSError  e   nil  NSArray  JSONarray    NSJSONSerialization JSONObjectWithData  data options  NSJSONReadingMutableContainers error   amp e           for int i 0 i lt  JSONarray count  i                          NSLog         JSONarray objectAtIndex i objectForKey   id                  NSLog         JSONarray objectAtIndex i objectForKey   name                 For swift 3 3        Pass The response data  amp  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

User · Answer

The following code fetches a JSON object from a webserver  and parses it to an NSDictionary  I have used the openweathermap API that returns a simple JSON response for this example  For keeping it simple  this code uses synchronous requests      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  amp response error nil      NSDictionary  res        NSJSONSerialization JSONObjectWithData GETReply options NSJSONReadingMutableLeaves   NSJSONReadingMutableContainers error nil      Nslog       res

User · Answer

The issue seems to be with autorelease of objects  NSJSONSerialization JSONObjectWithData is obviously creating some autoreleased objects and passing it back to you  If you try to take that on to a different thread  it will not work since it cannot be deallocated on a different thread   Trick might be to try doing a mutable copy of that dictionary or array and use it   NSError  e   nil  id jsonObject    NSJSONSerialization  JSONObjectWithData  data  options  NSJSONReadingMutableContainers  error   amp e  mutableCopy     Treating a NSDictionary as NSArray will not result in Bad access exception but instead will probably crash when a method call is made   Also  may be the options do not really matter here but it is better to give NSJSONReadingMutableContainers   NSJSONReadingMutableContainers   NSJSONReadingAllowFragments but even if they are autoreleased objects it may not solve this issue

User · Answer

It works for me  Your data object is probably nil and  as rckoenes noted  the root object should be a  mutable  array  See this code   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  amp e   NSLog        json      I had to escape the quotes in the JSON string with backslashes

User · Answer

NOTE  For Swift 3  Your JSON String is returning Array instead of Dictionary  Please try out the following             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  amp  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

User · Answer

Your root json object is not a dictionary but an array      id    1    name   Aaa      id    2    name   Bbb      This might give you a clear picture of how to handle it   NSError  e   nil  NSArray  jsonArray    NSJSONSerialization JSONObjectWithData  data options  NSJSONReadingMutableContainers error   amp e    if   jsonArray      NSLog   Error parsing JSON       e     else      for NSDictionary  item in jsonArray          NSLog   Item       item

User · Answer

rckoenes already showed you how to correctly get your data from the JSON string   To the question you asked  EXC BAD ACCESS almost always comes when you try to access an object after it has been  auto- released   This is not specific to JSON  de- serialization but  rather  just has to do with you getting an object and then accessing it after it s been released   The fact that it came via JSON doesn t matter   There are many-many pages describing how to debug this -- you want to Google  or SO  obj-c zombie objects and  in particular  NSZombieEnabled  which will prove invaluable to you in helping determine the source of your zombie objects     Zombie  is what it s called when you release an object but keep a pointer to it and try to reference it later

User · Answer

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

User · Answer

This is my code for checking if the received json is an array or dictionary   NSError  jsonError   nil  id jsonObject    NSJSONSerialization JSONObjectWithData jsonData options kNilOptions error  amp 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       I have tried this for options kNilOptions and NSJSONReadingMutableContainers and works correctly for both    Obviously  the actual code cannot be this way where I create the NSArray or NSDictionary pointer within the if-else block

User · Answer

bad example  should be something like this   id  1   name   something as name    number and string are mixed

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