Convert Dictionary to JSON in Swift

Question

I have create the next Dictionary   var postJSON    ids 0  answersArray 0   ids 1  answersArray 1   ids 2  answersArray 2   as Dictionary   and I get    2  B  1  A  3  C    So  how can I convert it to JSON

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private func convertDictToJson dict   NSDictionary  - gt  NSDictionary        var jsonDict   NSDictionary       do           let jsonData   try JSONSerialization data withJSONObject dict  options             let jsonDataString   String data  jsonData  encoding  String Encoding utf8           print  Post Request Params     jsonDataString            jsonDict    ParameterKey   jsonDataString          return jsonDict       catch           print  JSON serialization failed     error            jsonDict   nil           return jsonDict

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Sometimes it s necessary to print out server s response for debugging purposes  Here s a function I use   extension Dictionary        var json  String           let invalidJson    Not a valid JSON          do               let jsonData   try JSONSerialization data withJSONObject  self  options   prettyPrinted              return String bytes  jsonData  encoding  String Encoding utf8     invalidJson           catch               return invalidJson                      func printJson             print json             Example of use    lldb  po dictionary printJson        InviteId    2     EventId    13591     Messages                   SenderUserId    9514         MessageText     test          RecipientUserId    9470                     SenderUserId    9514         MessageText     test          RecipientUserId    9470               TargetUserId    9470     InvitedUsers          9470         InvitingUserId    9514     WillGo    true     DateCreated     2016-08-24 14 01 08  00 00

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Here s an easy extension to do this    https   gist github com stevenojo 0cb8afcba721838b8dcb115b846727c3  extension Dictionary       func jsonString   - gt  NSString            let jsonData   try  JSONSerialization data withJSONObject  self  options              guard jsonData    nil else  return nil          let jsonString   String data  jsonData   encoding   utf8          guard jsonString    nil else  return nil          return jsonString  as NSString

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Swift 3   let jsonData   try  JSONSerialization data withJSONObject  dict  options      let jsonString   String data  jsonData   encoding   utf8   print jsonString

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This works for me  import SwiftyJSON  extension JSON            mutating func appendIfKeyValuePair key  String  value  Any           if var dict   self dictionaryObject               dict key    value             self   JSON dict                     Usage  var data  JSON       data appendIfKeyValuePair key   quot myKey quot   value   quot myValue quot

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Swift 3 0  With Swift 3  the name of NSJSONSerialization and its methods have changed  according to the Swift API Design Guidelines   let dic     2    B    1    A    3    C    do       let jsonData   try JSONSerialization data withJSONObject  dic  options   prettyPrinted         here  jsonData  is the dictionary encoded in JSON data      let decoded   try JSONSerialization jsonObject with  jsonData  options             here  decoded  is of type  Any   decoded from JSON data         you can now cast it with the right type             if let dictFromJSON   decoded as   String String               use dictFromJSON         catch       print error localizedDescription        Swift 2 x  do       let jsonData   try NSJSONSerialization dataWithJSONObject dic  options  NSJSONWritingOptions PrettyPrinted         here  jsonData  is the dictionary encoded in JSON data      let decoded   try NSJSONSerialization JSONObjectWithData jsonData  options             here  decoded  is of type  AnyObject   decoded from JSON data         you can now cast it with the right type      if let dictFromJSON   decoded as   String String               use dictFromJSON         catch let error as NSError       print error        Swift 1  var error  NSError  if let jsonData   NSJSONSerialization dataWithJSONObject dic  options  NSJSONWritingOptions PrettyPrinted  error   amp error        if error    nil           println error        else              here  jsonData  is the dictionary encoded in JSON data          if let decoded   NSJSONSerialization JSONObjectWithData jsonData  options  nil  error   amp error  as   String String        if error    nil           println error        else              here  decoded  is the dictionary decoded from JSON data

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Swift 5  extension Dictionary                Convert Dictionary to JSON string         - Throws  exception if dictionary cannot be converted to JSON data or when data cannot be converted to UTF8 string         - Returns  JSON string     func toJson   throws - gt  String           let data   try JSONSerialization data withJSONObject  self          if let string   String data  data  encoding   utf8                return string                   throw NSError domain   quot Dictionary quot   code  1  userInfo    quot message quot    quot Data cannot be converted to  utf8 string quot

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You are making a wrong assumption  Just because the debugger Playground shows your dictionary in square brackets  which is how Cocoa displays dictionaries  that does not mean that is the way the JSON output is formatted  Here is example code that will convert a dictionary of strings to JSON  Swift 3 version  import Foundation  let dictionary     quot aKey quot    quot aValue quot    quot anotherKey quot    quot anotherValue quot   if let theJSONData   try  JSONSerialization data      withJSONObject  dictionary      options            let theJSONText   String data  theJSONData                                 encoding   ascii      print  quot JSON string     theJSONText   quot      To display the above in  quot pretty printed quot  format you d change the options line to      options    prettyPrinted   Or in Swift 2 syntax  import Foundation   let dictionary     quot aKey quot    quot aValue quot    quot anotherKey quot    quot anotherValue quot   let theJSONData   NSJSONSerialization dataWithJSONObject    dictionary     options  NSJSONWritingOptions 0     error  nil  let theJSONText   NSString data  theJSONData     encoding  NSASCIIStringEncoding  println  quot JSON string     theJSONText   quot    The output of that is  quot JSON string     quot anotherKey quot   quot anotherValue quot   quot aKey quot   quot aValue quot   quot   Or in pretty format       quot anotherKey quot     quot anotherValue quot      quot aKey quot     quot aValue quot     The dictionary is enclosed in curly braces in the JSON output  just as you d expect  EDIT  In Swift 3 4 syntax  the code above looks like this    let dictionary     quot aKey quot    quot aValue quot    quot anotherKey quot    quot anotherValue quot       if let theJSONData   try   JSONSerialization data        withJSONObject  dictionary        options   prettyPrinted                let theJSONText   String data  theJSONData                                 encoding  String Encoding ascii              print  quot JSON string    n  theJSONText  quot

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Answer for your question is below   Swift 2 1       do             if let postData   NSData   try NSJSONSerialization dataWithJSONObject dictDataToBeConverted  options  NSJSONWritingOptions PrettyPrinted              let json   NSString data  postData  encoding  NSUTF8StringEncoding   as String           print json                      catch              print error

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My answer for your question is below let dict     quot 0 quot    quot ArrayObjectOne quot    quot 1 quot    quot ArrayObjecttwo quot    quot 2 quot    quot ArrayObjectThree quot    var error   NSError   let jsonData   try  NSJSONSerialization dataWithJSONObject dict  options  NSJSONWritingOptions PrettyPrinted   let jsonString   NSString data  jsonData  encoding  String Encoding utf8 rawValue   as String  print jsonString   Answer is      quot 0 quot     quot ArrayObjectOne quot      quot 1 quot     quot ArrayObjecttwo quot      quot 2 quot     quot ArrayObjectThree quot

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using lldb  lldb  p JSONSerialization data withJSONObject  notification request content userInfo  options       Data   R16   375 bytes  lldb  p String data   R16   encoding   utf8    String   R18    quot    quot aps  quot     quot some text  quot   quot     or p String data  JSONSerialization data withJSONObject  notification request content userInfo  options        encoding   utf8    String   R4    quot    quot aps  quot     quot some text  quot   quot

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Swift 5   let dic     2    B    1    A    3    C   let encoder   JSONEncoder   if let jsonData   try  encoder encode dic        if let jsonString   String data  jsonData  encoding   utf8            print jsonString            Note that keys and values must implement Codable  Strings  Ints  and Doubles  and more  are already Codable  See Encoding and Decoding Custom Types

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Swift 4 Dictionary extension   extension Dictionary       var jsonStringRepresentation  String            guard let theJSONData   try  JSONSerialization data withJSONObject  self                                                              options    prettyPrinted   else               return nil                    return String data  theJSONData  encoding   ascii

[json] Convert Dictionary to JSON in Swift

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