How to parse nested json? Swift - ios

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

Answer 1

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)
}

Answer 2

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")])