Using Codable with object under single root key

While using codable we come across situations when our object keys are not at the root level

//Final code

/*
JSON data
{
  "dog": {
    "id": 1,
    "task": "bow wow"
  }
}*/

struct Dog: Codable {
  let id: Int
  let task: String
}

let decoder = JSONDecoder()
let userDictionary = try decoder.decode([String: Dog].self, from: jsonData)
let dogObj = userDictionary["dog"]

 

Now that we have our concerned properties “id” and “task” under “dog” key we can make our dog struct like

struct Dog: Codable {
  let id: Int
  let task: String
}

and a wrapper struct to take care  of outer “dog” key like

struct DogWrapper: Codable {
  let dog: Dog
}

this can be directly decoded from json like

let decoder = JSONDecoder()
let userDictionary = try decoder.decode(DogWrapper.self, from: jsonData)

this will give as a dogwrapper object with the dog as its property.

Now we can get dog object without wrapper struct by getting a dictionary of dog object for dog key. Because the JSON is theoretically “dog” object under “dog” key.So we can get it without DogWrapper as shown below

let decoder = JSONDecoder()
let userDictionary = try decoder.decode([String: Dog].self, from: jsonData)

Now the outer key “dog” has our Dog object as its value

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