How to convert a JSON string to a dictionary

Question

I want to make one function in my swift project that converts String to Dictionary json format but I got one error      Cannot convert expression s type   lvalue NSData options IntegerLitralConvertible       This is my code   func convertStringToDictionary  text String  - gt  Dictionary lt String String gt         var data  NSData   text dataUsingEncoding NSUTF8StringEncoding       var json  Dictionary   NSJSONSerialization JSONObjectWithData data  options 0  error  nil      return json      I make this function in Objective-C    -  NSDictionary  convertStringToDictionary  NSString  string     NSError  error      giving error as it takes dic  array etc only  not custom object    NSData  data    string dataUsingEncoding NSUTF8StringEncoding     id json    NSJSONSerialization JSONObjectWithData data options 0 error  amp error     return json

User · Answer

Swift 5   extension String       func convertToDictionary   - gt   String  Any             if let data   data using   utf8                return try  JSONSerialization jsonObject with  data  options      as   String  Any                    return nil

User · Answer

With Swift 3  JSONSerialization has a method called json Object with  options     json Object with  options    has the following declaration   class func jsonObject with data  Data  options opt  JSONSerialization ReadingOptions       throws - gt  Any      Returns a Foundation object from given JSON data    When you use json Object with  options     you have to deal with error handling  try  try  or try   and type casting  from Any   Therefore  you can solve your problem with one of the following patterns      1  Using a method that throws and returns a non-optional type  import Foundation  func convertToDictionary from text  String  throws - gt   String  String        guard let data   text data using   utf8  else   return           let anyResult  Any   try JSONSerialization jsonObject with  data  options          return anyResult as   String  String             Usage    let string1       City     Paris     do       let dictionary   try convertToDictionary from  string1      print dictionary     prints    City    Paris     catch       print error        let string2       Quantity   100   do       let dictionary   try convertToDictionary from  string2      print dictionary     prints       catch       print error        let string3       Object     do       let dictionary   try convertToDictionary from  string3      print dictionary    catch       print error     prints  Error Domain NSCocoaErrorDomain Code 3840  No value for key in object around character 9   UserInfo  NSDebugDescription No value for key in object around character 9          2  Using a method that throws and returns an optional type  import Foundation  func convertToDictionary from text  String  throws - gt   String  String         guard let data   text data using   utf8  else   return           let anyResult  Any   try JSONSerialization jsonObject with  data  options          return anyResult as   String  String      Usage   let string1       City     Paris     do       let dictionary   try convertToDictionary from  string1      print String describing  dictionary      prints  Optional   City    Paris      catch       print error        let string2       Quantity   100   do       let dictionary   try convertToDictionary from  string2      print String describing  dictionary      prints nil   catch       print error        let string3       Object     do       let dictionary   try convertToDictionary from  string3      print String describing  dictionary     catch       print error     prints  Error Domain NSCocoaErrorDomain Code 3840  No value for key in object around character 9   UserInfo  NSDebugDescription No value for key in object around character 9          3  Using a method that does not throw and returns a non-optional type  import Foundation  func convertToDictionary from text  String  - gt   String  String        guard let data   text data using   utf8  else   return           let anyResult  Any    try  JSONSerialization jsonObject with  data  options          return anyResult as   String  String             Usage   let string1       City     Paris     let dictionary1   convertToDictionary from  string1  print dictionary1     prints    City    Paris       let string2       Quantity   100   let dictionary2   convertToDictionary from  string2  print dictionary2     prints          let string3       Object     let dictionary3   convertToDictionary from  string3  print dictionary3     prints           4  Using a method that does not throw and returns an optional type  import Foundation  func convertToDictionary from text  String  - gt   String  String         guard let data   text data using   utf8  else   return nil       let anyResult   try  JSONSerialization jsonObject with  data  options          return anyResult as   String  String      Usage   let string1       City     Paris     let dictionary1   convertToDictionary from  string1  print String describing  dictionary1      prints  Optional   City    Paris        let string2       Quantity   100   let dictionary2   convertToDictionary from  string2  print String describing  dictionary2      prints  nil     let string3       Object     let dictionary3   convertToDictionary from  string3  print String describing  dictionary3      prints  nil

User · Answer

Swift 3   if let data   text data using  String Encoding utf8        do           let json   try JSONSerialization jsonObject with  data  options   mutableContainers  as   String Any          print json        catch           print  Something went wrong

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I ve updated Eric D s answer for Swift 5   func convertStringToDictionary text  String  - gt   String AnyObject         if let data   text data using   utf8            do               let json   try JSONSerialization jsonObject with  data  options   mutableContainers  as   String AnyObject              return json           catch               print  quot Something went wrong quot                       return nil

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let JSONData   jsonString data using   utf8    let jsonResult   try JSONSerialization jsonObject with  data  options   mutableLeaves   guard let userDictionary   jsonResult as  Dictionary lt String  AnyObject gt  else               throw NSError

User · Answer

I found code which converts the json string to NSDictionary or NSArray  Just add the extension   SWIFT 3 0  HOW TO USE  let jsonData    convertedJsonString as  String  parseJSONString   EXTENSION  extension String   var parseJSONString  AnyObject        let data   self data using  String Encoding utf8  allowLossyConversion  false      if let jsonData   data                  Will return an object or nil if JSON decoding fails         do                       let message   try JSONSerialization jsonObject with  jsonData  options  mutableContainers              if let jsonResult   message as  NSMutableArray                   return jsonResult   Will return the json array output               else if let jsonResult   message as  NSMutableDictionary                   return jsonResult   Will return the json dictionary output               else                   return nil                                 catch let error as NSError                       print  An error occurred    error                return nil                     else                  Lossless conversion of the string was not possible         return nil

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Swift 4  extension String       func convertToDictionary   - gt   String  Any             if let data   self data using   utf8                do                   return try JSONSerialization jsonObject with  data  options      as   String  Any                catch                   print error localizedDescription                                  return nil

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for swift 5  I write a demo to verify it   extension String            convert JsonString to Dictionary     func convertJsonStringToDictionary   - gt   String  Any             if let data   data using   utf8                return  try  JSONSerialization jsonObject with  data  options       as   String  Any                     return nil          let str       name     zgpeace     let dict   str convertJsonStringToDictionary   print  string  gt    str         string  gt    name   zgpeace   print  dicionary  gt    String describing  dict         dicionary  gt  Optional   name   zgpeace

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Details   Xcode Version 10 3  10G8   Swift 5   Solution  import Foundation     MARK  - CastingError  struct CastingError  Error       let fromType  Any Type     let toType  Any Type     init lt FromType  ToType gt  fromType  FromType Type  toType  ToType Type            self fromType   fromType         self toType   toType          extension CastingError  LocalizedError       var localizedDescription  String   return  Can not cast from   fromType  to   toType        extension CastingError  CustomStringConvertible   var description  String   return localizedDescription         MARK  - Data cast extensions  extension Data       func toDictionary options  JSONSerialization ReadingOptions       throws - gt   String  Any            return try to type   String  Any  self  options  options             func to lt T gt  type  T Type  options  JSONSerialization ReadingOptions       throws - gt  T           guard let result   try JSONSerialization jsonObject with  self  options  options  as  T else               throw CastingError fromType  type  toType  T self                    return result             MARK  - String cast extensions  extension String       func asJSON lt T gt  to type  T Type  using encoding  String Encoding    utf8  throws - gt  T           guard let data   data using  encoding  else   throw CastingError fromType  type  toType  T self            return try data to type  T self             func asJSONToDictionary using encoding  String Encoding    utf8  throws - gt   String  Any            return try asJSON to   String  Any  self  using  encoding              MARK  - Dictionary cast extensions  extension Dictionary       func toData options  JSONSerialization WritingOptions       throws - gt  Data           return try JSONSerialization data withJSONObject  self  options  options            Usage  let value1   try  data toDictionary   let value2   try  data to type   String  Any  self  let value3   try  data to type   String  String  self  let value4   try  string asJSONToDictionary   let value5   try  string asJSON to   String  String  self    Test sample     Do not forget to paste the solution code here   func testDescriber text  String  value  Any        print   n                                                 print  --   text  n n  type    type of  value   n  value    value       let json1   String  Any      key1    1   key2   true   key3      a   1   b   2    key4    1 2 3   var jsonData   try  json1 toData   testDescriber text   Sample test of func toDictionary     value  json1  if let data   jsonData       print    Result    String describing  try  data toDictionary          testDescriber text   Sample test of func to lt T gt    - gt   String  Any    value  json1  if let data   jsonData       print    Result    String describing  try  data to type   String  Any  self         testDescriber text   Sample test of func to lt T gt    - gt   String  with cast error   value  json1  if let data   jsonData       do           print    Result    String describing  try data to type   String  self            catch           print    ERROR    error             let array    1 4 5 6  testDescriber text   Sample test of func to lt T gt    - gt   Int    value  array  if let data   try  JSONSerialization data withJSONObject  array        print    Result    String describing  try  data to type   Int  self         let json2     key1    a    key2    b   testDescriber text   Sample test of func to lt T gt    - gt   String  String    value  json2  if let data   try  JSONSerialization data withJSONObject  json2        print    Result    String describing  try  data to type   String  String  self         let jsonString       key1      a      key2      b     testDescriber text   Sample test of func to lt T gt    - gt   String  String    value  jsonString  print    Result    String describing  try  jsonString asJSON to   String  String  self       testDescriber text   Sample test of func to lt T gt    - gt   String  String    value  jsonString  print    Result    String describing  try  jsonString asJSONToDictionary        let wrongJsonString       key1      a      key2      testDescriber text   Sample test of func to lt T gt    - gt   String  String  with JSONSerialization error   value  jsonString  do       let json   try wrongJsonString asJSON to   String  String  self      print    Result    String describing  json       catch       print    ERROR    error        Test log                                             -- Sample test of func toDictionary      type  Dictionary lt String  Any gt    value    key4    1  2  3    key2   true   key3     a   1   b   2    key1   1    Result  Optional   key4    lt   NSArrayI 0x600002a35380 gt   1  2  3      key2   1   key3         a   1      b   2      key1   1                                               -- Sample test of func to lt T gt    - gt   String  Any     type  Dictionary lt String  Any gt    value    key4    1  2  3    key2   true   key3     a   1   b   2    key1   1    Result  Optional   key4    lt   NSArrayI 0x600002a254d0 gt   1  2  3      key2   1   key1   1   key3         a   1      b   2                                                  -- Sample test of func to lt T gt    - gt   String  with cast error    type  Dictionary lt String  Any gt    value    key4    1  2  3    key2   true   key3     a   1   b   2    key1   1    ERROR  Can not cast from Array lt String gt  to Array lt String gt                                              -- Sample test of func to lt T gt    - gt   Int     type  Array lt Int gt    value   1  4  5  6    Result  Optional  1  4  5  6                                               -- Sample test of func to lt T gt    - gt   String  String     type  Dictionary lt String  String gt    value    key1    a    key2    b     Result  Optional   key1    a    key2    b                                                -- Sample test of func to lt T gt    - gt   String  String     type  String   value    key1    a    key2    b     Result  Optional   key1    a    key2    b                                                -- Sample test of func to lt T gt    - gt   String  String     type  String   value    key1    a    key2    b     Result  Optional   key1   a   key2   b                                               -- Sample test of func to lt T gt    - gt   String  String  with JSONSerialization error    type  String   value    key1    a    key2    b     ERROR  Error Domain NSCocoaErrorDomain Code 3840  Invalid value around character 21   UserInfo  NSDebugDescription Invalid value around character 21

User · Answer

Warning  this is a convenience method to convert a JSON string to a dictionary if  for some reason  you have to work from a JSON string  But if you have the JSON data available  you should instead work with the data  without using a string at all   Swift 3  func convertToDictionary text  String  - gt   String  Any         if let data   text data using   utf8            do               return try JSONSerialization jsonObject with  data  options      as   String  Any            catch               print error localizedDescription                      return nil    let str       name     James      let dict   convertToDictionary text  str    Swift 2  func convertStringToDictionary text  String  - gt   String AnyObject         if let data   text dataUsingEncoding NSUTF8StringEncoding            do               return try NSJSONSerialization JSONObjectWithData data  options      as   String AnyObject            catch let error as NSError               print error                      return nil    let str       name     James      let result   convertStringToDictionary str    Original Swift 1 answer   func convertStringToDictionary text  String  - gt   String String         if let data   text dataUsingEncoding NSUTF8StringEncoding            var error  NSError          let json   NSJSONSerialization JSONObjectWithData data  options  NSJSONReadingOptions allZeros  error   amp error  as   String String          if error    nil               println error                    return json           return nil    let str       name     James      let result   convertStringToDictionary str       name    James    if let name   result   name        The     is here because our  convertStringToDictionary  function returns an Optional     println name      James      In your version  you didn t pass the proper parameters to NSJSONSerialization and forgot to cast the result  Also  it s better to check for the possible error  Last note  this works only if your value is a String  If it could be another type  it would be better to declare the dictionary conversion like this   let json   NSJSONSerialization JSONObjectWithData data  options  NSJSONReadingOptions allZeros  error   amp error  as   String AnyObject    and of course you would also need to change the return type of the function   func convertStringToDictionary text  String  - gt   String AnyObject

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