Swift - Convert nested objects into an array of objects using decodable

Question

I have a JSON of following format in which there is a student object. student object has multiple students listed in it

Student {
    student1: {
        id: "12",
        name: "jack",
    },
    student2: {
        id: "2323",
        name: "lewis"
    },
    student3: {
        id: "1212",
        name: "pint"
    }
}

I would like to convert this into an array of student objects as shown below. How do i do this using decodable?

struct student: Decodable {
    let name: String
    let id: String
}

congnd · Accepted Answer · 2020-08-11 10:58:08Z

Perhaps this is what you want:

let json = """
{
  "student": {
      "student1": {
          "id": "12",
          "name": "jack",
      },
      "student2": {
          "id": "2323",
          "name": "lewis"
      },
      "student3": {
          "id": "1212",
          "name": "pint"
      }
  }
}
"""

struct Student: Decodable {
  let id: String
  let name: String
}

struct StudentContainer: Decodable {
  let students: [Student]

  private enum CodingKeys: String, CodingKey {
      case student
  }

  init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    let studentsDict = try container.decode([String: Student].self, forKey: .student)
    self.students = studentsDict.map { $0.value }
  }
}

let result = try? JSONDecoder().decode(StudentContainer.self, from: json.data(using: .utf8)!)

Robin · Accepted Answer · 2020-08-11 10:55:36Z

Apologies, I've misread this a bit so I'll have a go again.

To make an array you could do something like the following:

struct Students: Codable {
    let students: [Student]
}

struct Student: Codable {
    let name: String
    let id: String
}

This is enough to code the students into an array. Simply pass the JSON data with Students.

You will have to edit your JSON slightly, like this:

{
    "students": [
        {
            id: "12",
            name: "jack",
        },
        {
            id: "2323",
            name: "lewis"
        },
        {
            id: "1212",
            name: "pint"
        }
    ]
}

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