Reading in a JSON File Using Swift

Question

I m really struggling with trying to read a JSON file into Swift so I can play around with it  I ve spent the best part of 2 days re-searching and trying different methods but no luck as of yet so I have signed up to StackOverFlow to see if anyone can point me in the right direction       My JSON file is called test json and contains the following        person                   name    Bob           age    16           employed    No                         name    Vinny           age    56           employed    Yes                     The file is stored in the documents directly and I access it using the following code   let file    test json  let dirs   String     NSSearchPathForDirectoriesInDomains                                                            NSSearchpathDirectory DocumentDirectory                                                            NSSearchPathDomainMask AllDomainMask                                                            true  as String    if  dirs    nil        let directories  String     dirs     let dir   directories 0      let path   dir stringByAppendingPathComponent file     var jsonData   NSData contentsOfFile path  options  nil  error  nil  println  jsonData   jsonData      This prints what looks to be JSON encoded data   var jsonDict   NSJSONSerialization JSONObjectWithData jsonData  options  nil  error  nil  as  NSDictionary  println  jsonDict   jsonDict    - This prints nil         If anyone can just give me a push in the right direction on how I can de-serialize the JSON file and put it in an accessible Swift object I will be eternally grateful    Kind Regards   Krivvenz

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This worked great with me   func readjson fileName  String  - gt  NSData       let path   NSBundle mainBundle   pathForResource fileName  ofType   json       let jsonData   NSData contentsOfMappedFile  path        return jsonData

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The following code works for me  I am using Swift 5  let path   Bundle main path forResource   yourJSONfileName   ofType   json   var jsonData   try  String contentsOfFile  path   data using   utf8     Then  if your Person Struct  or Class  is Decodable  and also all of its properties   you can simply do   let person   try  JSONDecoder   decode Person self  from  jsonData    I avoided all the error handling code to make the code more legible

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I m providing another answer because none of the ones here are geared toward loading the resource from the test bundle  If you are consuming a remote service that puts out JSON and want to unit test parsing the results without hitting the actual service  you take one or more responses and put them into files in the Tests folder in your project   func testCanReadTestJSONFile         let path   NSBundle forClass  ForecastIOAdapterTests self  pathForResource  ForecastIOSample   ofType   json       if let jsonData   NSData contentsOfFile path             let json   JSON data  jsonData          if let currentTemperature   json  currently    temperature   double               println  json    json                XCTAssertGreaterThan currentTemperature  0                      This also uses SwiftyJSON but the core logic of getting the test bundle and loading the file is the answer to the question

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fileprivate class BundleTargetingClass    func loadJSON lt T gt  name  String  - gt  T      guard let filePath   Bundle for  BundleTargetingClass self  url forResource  name  withExtension   json   else       return nil        guard let jsonData   try  Data contentsOf  filePath  options   mappedIfSafe  else       return nil        guard let json   try  JSONSerialization jsonObject with  jsonData  options   allowFragments  else       return nil        return json as  T      copy-paste ready  3rd party framework independent solution   usage    let json   String   AnyObject     loadJSON name   Stations

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Swift 3 0  Xcode 8  iOS 10    if let path   Bundle main url forResource   person   withExtension   json              do               let jsonData   try Data contentsOf  path  options   mappedIfSafe              do                   if let jsonResult   try JSONSerialization jsonObject with  jsonData  options  JSONSerialization ReadingOptions rawValue  0   as  NSDictionary                       if let personArray   jsonResult value forKey   person   as  NSArray                           for     element  in personArray enumerated                                 if let element   element as  NSDictionary                                   let name   element value forKey   name   as  String                                 let age   element value forKey   age   as  String                                 let employed   element value forKey   employed   as  String                                 print  Name    name    age    age   employed    employed                                                                                                                  catch let error as NSError                   print  Error    error                            catch let error as NSError               print  Error    error                      Output   Name  Bob   age  16  employed  No Name  Vinny   age  56  employed  Yes

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Swift 5 1  Xcode 11 You can use this   struct Person   Codable       let name  String     let lastName  String     let age  Int    func loadJson fileName  String  - gt  Person       let decoder   JSONDecoder      guard         let url   Bundle main url forResource  fileName  withExtension   quot json quot            let data   try  Data contentsOf  url           let person   try  decoder decode Person self  from  data     else           return nil          return person

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I might also recommend Ray Wenderlich s Swift JSON Tutorial  which also covers the awesome SwiftyJSON alternative  Gloss   An excerpt  which granted  by itself  does not fully answer the poster  but the added value of this answer is the link  so no -1 s for that  please       In Objective-C  parsing and deserializing JSON is fairly straightforward    NSArray  json    NSJSONSerialization JSONObjectWithData JSONData options kNilOptions error nil   NSString  age   json 0    person     age    NSLog   Dani s age is      age        In Swift  parsing and deserializing JSON is a little more tedious due to Swift optionals and type-safety  but as  part of Swift 2 0 the guard statement was introduced to help get rid of nested if statements    var json  Array  do     json   try NSJSONSerialization JSONObjectWithData JSONData  options  NSJSONReadingOptions    as  Array   catch     print error     guard let item   json 0  as   String  AnyObject     let person   item  person   as   String  AnyObject     let age   person  age   as  Int else       return    print  Dani s age is   age      Of course  in XCode 8 x  you just double-tap the space bar and say  Hey  Siri  please deserialize this JSON for me in Swift 3 0 with space tab-indents

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Swift 4 using Decodable  struct ResponseData  Decodable       var person   Person    struct Person   Decodable       var name  String     var age  String     var employed  String    func loadJson filename fileName  String  - gt   Person         if let url   Bundle main url forResource  fileName  withExtension   json             do               let data   try Data contentsOf  url              let decoder   JSONDecoder               let jsonData   try decoder decode ResponseData self  from  data              return jsonData person           catch               print  error   error                        return nil     Swift 3  func loadJson filename fileName  String  - gt   String  AnyObject         if let url   Bundle main url forResource  fileName  withExtension   json             do               let data   try Data contentsOf  url              let object   try JSONSerialization jsonObject with  data  options   allowFragments              if let dictionary   object as   String  AnyObject                    return dictionary                         catch               print  Error   Unable to parse    fileName  json                       return nil

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Updated for Swift 3 with safest way      private func readLocalJsonFile          if let urlPath   Bundle main url forResource   test   withExtension   json              do               let jsonData   try Data contentsOf  urlPath  options   mappedIfSafe               if let jsonDict   try JSONSerialization jsonObject with  jsonData  options   mutableContainers  as   String  AnyObject                     if let personArray   jsonDict  person   as    String  AnyObject                          for personDict in personArray                            for  key  value  in personDict                                print key  value                                                    print   n                                                                            catch let jsonError               print jsonError

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Swift 4 JSON to Class with Decodable - for those who prefer classes  Define the classes as follows   class People  Decodable     var person   Person      init fileName   String          url  data and jsonData should not be nil     guard let url   Bundle main url forResource  fileName  withExtension   json   else   return       guard let data   try  Data contentsOf  url  else   return       guard let jsonData   try  JSONDecoder   decode People self  from  data  else   return           assigns the value to  person      person   jsonData person        class Person   Decodable     var name  String   var age  String   var employed  String     Usage  pretty abstract   let people   People fileName   people   let personArray   people person   This allow methods for both People and Person classes  variables  attributes  and methods can also marked as private if needed

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Here is my solution using SwiftyJSON  if let path   String   NSBundle mainBundle   pathForResource  filename   ofType   json         if let data   NSData contentsOfFile  path             let json   JSON data  data

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Xcode 8 Swift 3 read json from file update       if let path   Bundle main path forResource   userDatabseFakeData   ofType   json             do               let jsonData   try NSData contentsOfFile  path  options  NSData ReadingOptions mappedIfSafe              do                   let jsonResult  NSDictionary   try JSONSerialization jsonObject with  jsonData as Data  options  JSONSerialization ReadingOptions mutableContainers  as  NSDictionary                 if let people    NSDictionary    jsonResult  person   as   NSDictionary                        for person  NSDictionary in people                           for  name value  in person                               print    name      value                                                                                    catch              catch

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I   ve used below code to fetch JSON from FAQ-data json file present in project directory    I   m implementing in Xcode 7 3 using Swift        func fetchJSONContent                 if let path   NSBundle mainBundle   pathForResource  FAQ-data   ofType   json                      if let jsonData   NSData contentsOfFile  path                        do                           if let jsonResult  NSDictionary   try NSJSONSerialization JSONObjectWithData jsonData  options  NSJSONReadingOptions MutableContainers  as  NSDictionary                                if let responseParameter   NSDictionary   jsonResult  responseParameter   as  NSDictionary                                    if let response   NSArray   responseParameter  FAQ   as  NSArray                                       responseFAQ   response                                     print  response FAQ     response                                                                                                                                        catch   print  Error while parsing    error                                                 override func viewWillAppear animated  Bool            fetchFAQContent           Structure of JSON file           status    00        msg    FAQ List         responseParameter              FAQ                                                    question      Question No 1 here                      answer      Answer goes here                        id   1                                                               question      Question No 2 here                      answer      Answer goes here                      id   2

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Follow the below code    if let path   NSBundle mainBundle   pathForResource  test   ofType   json         if let jsonData   NSData contentsOfFile  path  options   DataReadingMappedIfSafe  error  nil                if let jsonResult  NSDictionary   NSJSONSerialization JSONObjectWithData jsonData  options  NSJSONReadingOptions MutableContainers  error  nil  as  NSDictionary                       if let persons   NSArray   jsonResult  person   as  NSArray                                  Do stuff                                    The array  persons  will contain all data for key person  Iterate throughs to fetch it   Swift 4 0   if let path   Bundle main path forResource   test   ofType   json         do             let data   try Data contentsOf  URL fileURLWithPath  path   options   mappedIfSafe            let jsonResult   try JSONSerialization jsonObject with  data  options   mutableLeaves            if let jsonResult   jsonResult as  Dictionary lt String  AnyObject gt   let person   jsonResult  person   as   Any                           do stuff                     catch                 handle error

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If anyone is looking for SwiftyJSON Answer  Update  For Swift 3 4   if let path   Bundle main path forResource   assets test   ofType   json         do           let data   try Data contentsOf  URL fileURLWithPath  path   options   alwaysMapped          let jsonObj   try JSON data  data          print  jsonData   jsonObj          catch let error           print  parse error    error localizedDescription            else       print  Invalid filename path

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Latest swift 3 0 absolutely working   func loadJson filename fileName  String  - gt   String  AnyObject         if let url   Bundle main url forResource  fileName  withExtension   json            if let data   NSData contentsOf  url              do                       let object   try JSONSerialization jsonObject with  data as Data  options   allowFragments                      if let dictionary   object as   String  AnyObject                            return dictionary                                         catch                       print  Error   Unable to parse    fileName  json                                               print  Error   Unable to load    fileName  json                     return nil

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This worked for me with XCode 8 3 3  func fetchPersons         if let pathURL   Bundle main url forResource   Person   withExtension   json             do                let jsonData   try Data contentsOf  pathURL  options   mappedIfSafe               let jsonResult   try JSONSerialization jsonObject with  jsonData  options   mutableContainers  as   String  Any              if let persons   jsonResult  person   as   Any                    print persons                          catch let error               print  error localizedDescription

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Simplifying the example provided by Peter Kreinz  Works with Swift 4 2   The extension function   extension Decodable     static func parse jsonFile  String  - gt  Self        guard let url   Bundle main url forResource  jsonFile  withExtension   json              let data   try  Data contentsOf  url             let output   try  JSONDecoder   decode self  from  data          else         return nil            return output         The example model   struct Service  Decodable     let name  String     The example usage       service json        name    Home  amp  Garden     guard let output   Service parse jsonFile   service   else      do something if parsing failed  return       use output if all good   The example will work with arrays  too       services json          name    Home  amp  Garden       guard let output    Service  parse jsonFile   services   else      do something if parsing failed  return       use output if all good   Notice how we don t provide any unnecessary generics  thus we don t need to cast the result of parse

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Swift 4 1 Updated Xcode 9 2  if let filePath   Bundle main path forResource   fileName   ofType   json    let data   NSData contentsOfFile  filePath          do         let json   try JSONSerialization jsonObject with  data as Data  options  JSONSerialization ReadingOptions allowFragments                         catch                     Handle error

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change type based on your struct and right JSON file  let quoteData   DataType        load  file json    func load lt T  Decodable gt    filename  String  as type  T Type   T self  - gt  T       let data  Data      guard let file   Bundle main url forResource  filename  withExtension  nil          else               fatalError  Couldn t find   filename  in main bundle               do           data   try Data contentsOf  file        catch           fatalError  Couldn t load   filename  from main bundle  n  error               do           let decoder   JSONDecoder           return try decoder decode T self  from  data        catch           fatalError  Couldn t parse   filename  as   T self   n  error

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SWIFTYJSON VERSION SWIFT 3  func loadJson fileName  String  - gt  JSON        var dataPath JSON       if let path   String   Bundle main path forResource  fileName  ofType   json             if let data   NSData contentsOfFile  path                 dataPath   JSON data  data as Data                      return dataPath

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Swift 2 1 answer  based on Abhishek s         if let path   NSBundle mainBundle   pathForResource  test   ofType   json             do               let jsonData   try NSData contentsOfFile  path  options  NSDataReadingOptions DataReadingMappedIfSafe              do                   let jsonResult  NSDictionary   try NSJSONSerialization JSONObjectWithData jsonData  options  NSJSONReadingOptions MutableContainers  as  NSDictionary                 if let people    NSDictionary    jsonResult  person   as   NSDictionary                        for person  NSDictionary in people                           for  name value  in person                               print    name      value                                                                                    catch              catch

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First create a Struc codable like this     struct JuzgadosList   Codable       var CP   Int     var TEL   String     var LOCAL   String     var ORGANO   String     var DIR   String     Now declare the variable   var jzdosList    JuzgadosList      Read from main directory  func getJsonFromDirectory              if let path   Bundle main path forResource   juzgados   ofType   json                 do                   let data   try Data contentsOf  URL fileURLWithPath  path   options   alwaysMapped                  let jList   try JSONDecoder   decode  JuzgadosList  self  from  data                  self jzdosList   jList                  DispatchQueue main async        - gt  Void in                     self tableView reloadData                                    catch let error                   print  parse error    error localizedDescription                            else               print  Invalid filename path                      Read from web  func getJsonFromUrl             self jzdosList removeAll keepingCapacity  false           print  Internet Connection Available             guard let url   URL string   yourURL    else   return            let request   URLRequest url  url  cachePolicy  URLRequest CachePolicy reloadIgnoringLocalCacheData  timeoutInterval  60 0          URLSession shared dataTask with  request     data  response  err  in             guard let data   data else   return               do                   let jList   try JSONDecoder   decode  JuzgadosList  self  from  data                  self jzdosList   jList                  DispatchQueue main async        - gt  Void in                     self tableView reloadData                                   catch let jsonErr                   print  Error serializing json    jsonErr                          resume

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Use this generic function  func readJSONFromFile lt T  Decodable gt  fileName  String  type  T Type  - gt  T        if let url   Bundle main url forResource  fileName  withExtension   json             do               let data   try Data contentsOf  url              let decoder   JSONDecoder               let jsonData   try decoder decode T self  from  data              return jsonData           catch               print  error   error                        return nil     with this line of code   let model   readJSONFromFile fileName   Model   type  Model self    for this type   struct Model  Codable       let tall  Int

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Based on Abhishek s answer  for iOS 8 this would be   let masterDataUrl  NSURL   NSBundle mainBundle   URLForResource  masterdata   withExtension   json    let jsonData  NSData   NSData contentsOfURL  masterDataUrl   let jsonResult  NSDictionary   NSJSONSerialization JSONObjectWithData jsonData  options  nil  error  nil  as  NSDictionary var persons   NSArray   jsonResult  person   as  NSArray

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Swift 4  Try out my solution      test json          person                           name    Bob                age    16                employed    No                                    name    Vinny                age    56                employed    Yes                         RequestCodable swift   import Foundation  struct RequestCodable Codable       let person  PersonCodable         PersonCodable swift   import Foundation  struct PersonCodable Codable       let name String     let age String     let employed String        Decodable FromJSON swift   import Foundation  extension Decodable        static func fromJSON lt T Decodable gt    fileName  String  fileExtension  String  json   bundle  Bundle    main  throws - gt  T           guard let url   bundle url forResource  fileName  withExtension  fileExtension  else               throw NSError domain  NSURLErrorDomain  code  NSURLErrorResourceUnavailable                     let data   try Data contentsOf  url           return try JSONDecoder   decode T self  from  data               Example    let result   RequestCodable fromJSON  test   as RequestCodable   result  person compactMap   print  0          PersonCodable name   Bob   age   16   employed   No   PersonCodable name   Vinny   age   56   employed   Yes

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Updated names for Swift 3 0  Based on Abhishek s answer and Druva s answer  func loadJson forFilename fileName  String  - gt  NSDictionary         if let url   Bundle main url forResource  fileName  withExtension   json             if let data   NSData contentsOf  url                do                   let dictionary   try JSONSerialization jsonObject with  data as Data  options   allowFragments  as  NSDictionary                  return dictionary               catch                   print  Error   Unable to parse    fileName  json                                   print  Error   Unable to load    fileName  json              return nil

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