Swift – Codable

what is it

  • Allows creation of Swift object directly from JSON and vice versa
  • Introduced in Swift 4.0

How to use:

  • Derive your class/struct from Codeable
 struct Student : Codable {
	var name : String
	var roll_no: String
	var class : String
 }
  • Creating swift object from JSON string
let jsonData = jsonString.data(using: .utf8)
    let student = try JSONDecoder().decoder (Student.self, from jsonData)
    print (student.name)
  • use CodingKey when the Json variable is different from struct variable name
 struct Student : Codable {
	var name : String
	var rollNo: String
	var class : String

	enum CodingKeys: String, CodingKey {
       	 case name = “student_name”
       	 case rollNo = “roll_no”
       	 case class
   	 }

 }
  • Encoding is equally straight forward
let jsonData = try! JSONEncoder().encode(student)
let jsonString = String(data: jsonData, encoding: .utf8)!
  • Working with array of objects
let students = try! JSONDecoder().decode([Student].self, from: jsonData)
  • Working with nested objects
    Its just the same, as with simple objects, define nested struct and ensure using top level struct (which also should be a Codeable) to encode/decode

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