Codable protocol for JSON parsing in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a struct that can be encoded and decoded from JSON.

iOS Swift

struct User: [1] {
  var name: String
  var age: Int
}

Drag options to blanks, or click blank then click option'

AIdentifiable

BCodable

CEquatable

DHashable

Attempts:

3 left

💡 Hint

Common Mistakes

Using Equatable instead of Codable.

Forgetting to conform to any protocol.

The Codable protocol allows the struct to be encoded to and decoded from JSON easily.

2fill in blank

medium

Complete the code to decode JSON data into a User instance.

iOS Swift

let decoder = JSONDecoder()
let user = try decoder.[1](User.self, from: jsonData)

Drag options to blanks, or click blank then click option'

Aencode

Bparse

Cdecode

Dserialize

Attempts:

3 left

💡 Hint

Common Mistakes

Using encode instead of decode.

Trying to use parse or serialize which are not JSONDecoder methods.

The decode method of JSONDecoder converts JSON data into a Swift object.

3fill in blank

hard

Fix the error in the decoding code by completing the blank.

iOS Swift

do {
  let user = try JSONDecoder().decode([1], from: data)
  print(user.name)
} catch {
  print("Failed to decode")
}

Drag options to blanks, or click blank then click option'

AUser() -> User

BUser()

CUser.Type

DUser.self

Attempts:

3 left

💡 Hint

Common Mistakes

Passing an instance like User() instead of the type.

Using User.Type which is a metatype but not the correct syntax here.

The decode method requires the type itself, not an instance, so use User.self.

4fill in blank

hard

Fill both blanks to encode a User instance into JSON data.

iOS Swift

let encoder = JSONEncoder()
let jsonData = try encoder.[1]([2])

Drag options to blanks, or click blank then click option'

Aencode

Buser

Cdecode

DUser.self

Attempts:

3 left

💡 Hint

Common Mistakes

Using decode instead of encode.

Passing the type User.self instead of the instance user.

Use encode to convert the user instance into JSON data.

5fill in blank

hard

Fill all three blanks to create a dictionary from JSON data using Codable.

iOS Swift

struct Item: Codable {
  var id: Int
  var name: String
}

let items = try JSONDecoder().decode([[1]].self, from: [2])
let dict = Dictionary(uniqueKeysWithValues: items.map { ($0.[3], $0.name) })

Drag options to blanks, or click blank then click option'

AItem

BjsonData

Cid

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong type in decode.

Passing wrong variable names in map closure.

Decode an array of Item from jsonData. Then map each item using its id as the key.