How to parse nested json? Swift

Question

i have a local json string and i am trying to parse it but when i try to do so, i am constantly getting an error. I have also seen this error in nested dictionary but couldnt find an error. Below is the json string

let jsonNestedString  = "{\"meta\":{\"page\":1,\"total_pages\":4,\"per_page\":10,\"total_records\" : 38}, \"reweries\":[\"id\":1234,\"name\":\"saintArnold\"},{\"id\":52892,\"name\":\"buffalo bayou\"]}"

i am doing this process via Codable and below is the struct i have created for the same

struct PagedBreweries:Codable{
    struct Meta:Codable{
        let page : Int
        let total_pages:Int
        let per_page:Int
        let total_records: Int
        enum CodingKeys: String, CodingKey{
            case page
            case total_pages
            case per_page
            case total_records
        }
    }

    struct Brewery :Codable{
        let id:Int
        let name:String

    }
    let meta:Meta
    let breweries :[Brewery]
}

then this data is parsed to a function as below

    func jsonNested(){
    let jsonData = jsonNestedString.data(using: .utf8)
    let decoder = JSONDecoder()
    let data  = try! decoder.decode(PagedBreweries.Meta.self, from: jsonData!)
    print(data)
}

and when i try to build, the error i get is present in try! decoder.decode
command and the error is

Thread 1: Fatal error: 'try!' expression unexpectedly raised an error: Swift.DecodingError.keyNotFound(CodingKeys(stringValue: "page", intValue: nil), Swift.DecodingError.Context(codingPath: [], debugDescription: "No value associated with key CodingKeys(stringValue: \"page\", intValue: nil) (\"page\").", underlyingError: nil))

Could any one provide a solution? Thanks in advance

This might not be the cause, but the `]age` part looks a little bit suspicious. — Cristik, Jan 09 '19 at 12:11
Your JSON isn't valid. You should always test your JSON on a validator like [this](https://jsonformatter.curiousconcept.com) before trying to use it. — Dávid Pásztor, Jan 09 '19 at 12:13
i tried on a json validator and it confirms that this json is in fact valid — vgvishesh23113, Jan 09 '19 at 12:18
This part is also not valid: `\"reweries\":[\"id\":1234,\"name\":\"saintArnold\"}`. — Cristik, Jan 09 '19 at 12:31
**Read** the error message, it's pretty descriptive: Character 64 is the region around `= 38`.Key/value pairs in JSON are always separated by **colon** (`:`). And about 20 characters later there is an opening brace missing after `:[` — vadian, Jan 09 '19 at 12:31
No, there is none. It must be `...\"reweries\":[{\"id\"...`. By the way there's also a `b` missing, you probably mean `\"breweries\"` — vadian, Jan 09 '19 at 12:44
Possible duplicate of [How to decode a nested JSON struct with Swift Decodable protocol?](https://stackoverflow.com/questions/44549310/how-to-decode-a-nested-json-struct-with-swift-decodable-protocol) — Hamish, Jan 09 '19 at 13:05

Shehata Gamal · Answer 1 · 2019-01-09T12:40:23.163

3

Correct json

{
    "meta": {
        "page": 1,
        "total_pages": 4,
        "per_page": 10,
        "total_records": 38
    },
    "reweries": [{
    "id": 1234,
    "name": "saintArnold"
    },
    {
    "id": 52892,
    "name": "buffalo bayou"
    }
    ]
}

struct Root: Codable {
    let meta: Meta
    let reweries: [Rewery]
}

struct Meta: Codable {
    let page, totalPages, perPage, totalRecords: Int

    enum CodingKeys: String, CodingKey {  // snake case may be used 
        case age = "page"
        case totalPages = "total_pages"
        case perPage = "per_page"
        case totalRecords = "total_records"
    }
}

struct Rewery: Codable {
    let id: Int
    let name: String
}

  let jsonNestedString  = """
    {\"meta\":{\"page\":1,\"total_pages\":4,\"per_page\":10,\"total_records\":38}, \"reweries\":[{\"id\":1234,\"name\":\"saintArnold\"},{\"id\":52892,\"name\":\"buffalo bayou\"}]}
"""

  // or 

let jsonNestedString  = """

{
    "meta": {
        "page": 1,
        "total_pages": 4,
        "per_page": 10,
        "total_records": 38
    },
    "reweries": [{
    "id": 1234,
    "name": "saintArnold"
    },
    {
    "id": 52892,
    "name": "buffalo bayou"
    }
    ]
}


"""

do {

    let jsonData = jsonNestedString.data(using: .utf8)
    let decoder = JSONDecoder()
    let data  = try decoder.decode(Root.self, from: jsonData!)
    print(data)


} catch  {
    print(error)
}

edited Jan 09 '19 at 12:40

answered Jan 09 '19 at 12:22

Shehata Gamal

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my json is valid i have tested on multiple sites but still gives the same error – vgvishesh23113 Jan 09 '19 at 12:24
also, you have changed the code, the above structures as you suggest are not nested – vgvishesh23113 Jan 09 '19 at 12:25
@vgvishesh23113 i don't know why you need the slashes , but i added them see edit....... – Shehata Gamal Jan 09 '19 at 12:35
i need slashes to make it a valid string in swift – vgvishesh23113 Jan 09 '19 at 12:37
no you don't have to there is a multi line string with """str""" see edit........... – Shehata Gamal Jan 09 '19 at 12:39
i know that now, didnt before but it shud still work right as slashes were suggessted by swift itself – vgvishesh23113 Jan 09 '19 at 12:41
if you use "" then you have too , but with """ escape them – Shehata Gamal Jan 09 '19 at 12:41
still does not help with the error, any insights for that?? – vgvishesh23113 Jan 09 '19 at 12:43
@vgvishesh23113 did you tried all answer content ?? – Shehata Gamal Jan 09 '19 at 12:50
in that case i apologize, i might have changed something in your answer which didnt solve it. once again , thanks for the time and effort, much appreciated – vgvishesh23113 Jan 09 '19 at 12:58

vadian · Accepted Answer · 2019-01-09T13:09:31.970

The JSON is corrupt and you are decoding the wrong root object.

This is the correct JSON being decoded with your structs and conforming to the Swift naming convention

let jsonNestedString  = """
{"meta":{"page":1,"total_pages":4,"per_page":10,"total_records" : 38}, "breweries":[{"id":1234,"name":"saintArnold"},{"id":52892,"name":"buffalo bayou"}]}
"""

struct PagedBreweries : Codable {
    struct Meta : Codable {
        let page : Int
        let totalPages:Int
        let perPage:Int
        let totalRecords: Int
    }

    struct Brewery : Codable {
        let id:Int
        let name:String

    }
    let meta:Meta
    let breweries :[Brewery]
}

func jsonNested(){
    let jsonData = Data(jsonNestedString.utf8)
    let decoder = JSONDecoder()
    decoder.keyDecodingStrategy = .convertFromSnakeCase
    let data  = try! decoder.decode(PagedBreweries.self, from: jsonData)
    print(data)
}

jsonNested()

// Printed result: 
// PagedBreweries(meta: __lldb_expr_1.PagedBreweries.Meta(page: 1, totalPages: 4, perPage: 10, totalRecords: 38), breweries: [__lldb_expr_1.PagedBreweries.Brewery(id: 1234, name: "saintArnold"), __lldb_expr_1.PagedBreweries.Brewery(id: 52892, name: "buffalo bayou")])

it finally worked, thank you so much for your time pal – vgvishesh23113 Jan 09 '19 at 12:53 — vgvishesh23113, Jan 09 '19 at 12:53

How to parse nested json? Swift

2 Answers2