Converting JSON array string to JSON array returns null

Question

I use alamofire for requests. Here on a simple response, I'm getting this JSON string from alamofire

Optional("[{\"nl2br\":\"2019-05-02 19:52:10\",\"nl3br\":\"\",\"nl4br\":\"#lxr\",\"nl5br\":\"1\",\"nl6br\":\"nein\",\"nl7br\":\"bARxrdw9c7WS1RN9c\\/\\/MrA==822b5dd20cb73611:35cab43d0c7e82e73c62818d9f90cfe8\",\"nl8br\":\"tBDSzkQ7eCNERwldgZiwKg==a7590d9d8affdbe5:63b9a9bf6421ea7db2a55f8773990b08\",\"nl9br\":\"fpd17pxVUzcJWNskVWyBeA==cf21783de8334248:a93e8b8a92ef9b238b75ad87a315ce3e\"},{\"nl2br\":\"2019-04-26 21:36:32\",\"nl3br\":\"old\",\"nl4br\":\"\",\"nl5br\":null,\"nl6br\":\"ja\",\"nl7br\":\"emjUIzK92fWwHNLv\\/4xv2Q==8fca202c9a816c7b:655ef8aaaa0212bb9e77a9c35a56c3a7\",\"nl8br\":\"1C5Hy\\/ZhMk3b6SZY8c08lw==cb3b0f4fdd6b5957:034e72d400598fedc43b3111d841a31b\",\"nl9br\":\"KUfLHbih9612dhNCYPOrTg==48da9c3362430e01:3a80ba9fb516e4172aa39b017abcd96e\"},{\"nl2br\":\"2019-04-26 21:20:24\",\"nl3br\":\"holder\",\"nl4br\":\"\",\"nl5br\":null,\"nl6br\":\"ja\",\"nl7br\":\"J59nMBWUMyU9PzdbwQqd0g==f7d3c6c561c33f0b:3465e9131a2577c39cddcc606d0785b0\",\"nl8br\":\"G4rRevk951ZBJJQKzBeJZg==45c0ebcdc1e000e8:dc770c3849fef8b058f85cad42c73e1d\",\"nl9br\":\"338Ud9CIDgnyBV96F2Fx\\/w==d0f825064e0ecf81:0ca00ff27e977ef5f8123d38c643a8b3\"},{\"nl2br\":\"2019-04-10 23:57:17\",\"nl3br\":\"\",\"nl4br\":\"Wasmes, here\'s a video and do ya need?\",\"nl5br\":\"1\",\"nl6br\":\"ja\",\"nl7br\":\"fw17O1L9SuO9FS3qu6U7QQ==706bd09ee3b5ec55:6667d9020a0edcacbd217f631d2305c0\",\"nl8br\":\"2tTE9+0Kr6cVSuEOsq8h0w==3e0e46352da323be:941710bd881546dfa08d3afb6aea2831\",\"nl9br\":\"NAkMx0OsKwXVGndYXbAFmA==1234c0b2992502bf:666f8efd3bdf8ee8b0a2ee4e7222c2ef\"},{\"nl2br\":\"2019-02-22 21:38:16\",\"nl3br\":\"i\'m giving up on you,  but don\'t \",\"nl4br\":\"\",\"nl5br\":null,\"nl6br\":\"nein\",\"nl7br\":\"gOv13Dsxf1N2UG46KT3tvQ==dd02a83b1837bb24:4f7c7ab95e873d35685ab7b738626f44\",\"nl8br\":\"40+GOpcNU6M4F688DJyxFA==70bc177842f3f6cf:232b065423bd2683d75ca177775fd352\",\"nl9br\":\"mBc3pEHKBiiPeAEpZRskug==71b353fed6403b99:c58099676beacc146c14867645e29783\"}]")

I get my data like this and convert it like this

if let responseData = response.data {
  let responseDataString = String(data: responseData, encoding:String.Encoding(rawValue: String.Encoding.utf8.rawValue))
  print(responseDataString) // gives the whole string above
  if let obj = responseDataString?.toJSON() as? [String:AnyObject] {
    print(obj["nl2br"] as! String) // gives nothing, just nil
  }
}

My string extension is like this.

extension String {
    func toJSON() -> Any? {
        guard let data = self.data(using: .utf8, allowLossyConversion: false) else { return nil }
        return try? JSONSerialization.jsonObject(with: data, options: .mutableContainers)
    }
}

Any idea why this behaviour is expected? I tried printing obj that gives nothing too.

Unrelated but , encoding:String.Encoding(rawValue: String.Encoding.utf8.rawValue)) is hilarious syntax. Why not simply , encoding: .utf8)? And why .mutableContainers? All .mutable... reading options are pointless in Swift. Omit the parameter. — vadian
– vadian, Commented Jun 24, 2019 at 16:19

Community · Accepted Answer · 2020-06-20 09:12:55Z

Your root is an array not a dictionary Change responseDataString?.toJSON() as? [[String:Any]]

extension String {
    func toJSON() -> Any? {
        return try? JSONSerialization.jsonObject(with: Data(self.utf8))
    }
}

let responseDataString:String? =  """[{\"nl2br\":\"2019-05-02 19:52:10\",\"nl3br\":\"\",\"nl4br\":\"#lxr\",\"nl5br\":\"1\",\"nl6br\":\"nein\",\"nl7br\":\"bARxrdw9c7WS1RN9c\\/\\/MrA==822b5dd20cb73611:35cab43d0c7e82e73c62818d9f90cfe8\",\"nl8br\":\"tBDSzkQ7eCNERwldgZiwKg==a7590d9d8affdbe5:63b9a9bf6421ea7db2a55f8773990b08\",\"nl9br\":\"fpd17pxVUzcJWNskVWyBeA==cf21783de8334248:a93e8b8a92ef9b238b75ad87a315ce3e\"},{\"nl2br\":\"2019-04-26 21:36:32\",\"nl3br\":\"old\",\"nl4br\":\"\",\"nl5br\":null,\"nl6br\":\"ja\",\"nl7br\":\"emjUIzK92fWwHNLv\\/4xv2Q==8fca202c9a816c7b:655ef8aaaa0212bb9e77a9c35a56c3a7\",\"nl8br\":\"1C5Hy\\/ZhMk3b6SZY8c08lw==cb3b0f4fdd6b5957:034e72d400598fedc43b3111d841a31b\",\"nl9br\":\"KUfLHbih9612dhNCYPOrTg==48da9c3362430e01:3a80ba9fb516e4172aa39b017abcd96e\"},{\"nl2br\":\"2019-04-26 21:20:24\",\"nl3br\":\"holder\",\"nl4br\":\"\",\"nl5br\":null,\"nl6br\":\"ja\",\"nl7br\":\"J59nMBWUMyU9PzdbwQqd0g==f7d3c6c561c33f0b:3465e9131a2577c39cddcc606d0785b0\",\"nl8br\":\"G4rRevk951ZBJJQKzBeJZg==45c0ebcdc1e000e8:dc770c3849fef8b058f85cad42c73e1d\",\"nl9br\":\"338Ud9CIDgnyBV96F2Fx\\/w==d0f825064e0ecf81:0ca00ff27e977ef5f8123d38c643a8b3\"},{\"nl2br\":\"2019-04-10 23:57:17\",\"nl3br\":\"\",\"nl4br\":\"Wasmes, here\'s a video and do ya need?\",\"nl5br\":\"1\",\"nl6br\":\"ja\",\"nl7br\":\"fw17O1L9SuO9FS3qu6U7QQ==706bd09ee3b5ec55:6667d9020a0edcacbd217f631d2305c0\",\"nl8br\":\"2tTE9+0Kr6cVSuEOsq8h0w==3e0e46352da323be:941710bd881546dfa08d3afb6aea2831\",\"nl9br\":\"NAkMx0OsKwXVGndYXbAFmA==1234c0b2992502bf:666f8efd3bdf8ee8b0a2ee4e7222c2ef\"},{\"nl2br\":\"2019-02-22 21:38:16\",\"nl3br\":\"i\'m giving up on you,  but don\'t \",\"nl4br\":\"\",\"nl5br\":null,\"nl6br\":\"nein\",\"nl7br\":\"gOv13Dsxf1N2UG46KT3tvQ==dd02a83b1837bb24:4f7c7ab95e873d35685ab7b738626f44\",\"nl8br\":\"40+GOpcNU6M4F688DJyxFA==70bc177842f3f6cf:232b065423bd2683d75ca177775fd352\",\"nl9br\":\"mBc3pEHKBiiPeAEpZRskug==71b353fed6403b99:c58099676beacc146c14867645e29783\"}]"""
if let obj = responseDataString?.toJSON() as? [[String:Any]] { 
   obj.forEach {
     print($0["nl2br"])
   } 
}

Result

Optional(2019-05-02 19:52:10)

Optional(2019-04-26 21:36:32)

Optional(2019-04-26 21:20:24)

Optional(2019-04-10 23:57:17)

Optional(2019-02-22 21:38:16)

Edit: In json this

[{ 
   "name":"ppp"
}]

is an array of dictionaries to be [[String:Any]] notice nested [[]] , while this

{ 
   "name":"ppp"
}

is a dictionary represented by [String:Any] notice only []

[String:AnyObject] is a dictionary, and [String:AnyObject] is a array's dictionary, not?

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