why does swift 4 codable throw an error when parsing [duplicate] - ios

Question

This question already has answers here:
Using codable with value that is sometimes an Int and other times a String
(5 answers)
Closed 4 years ago.
This is my first time using the swift 4 codable protocol in an app.
I'm given a json response like this -
{
"result": [
{
"id": 1,
"heading": "Chapter 1",
"headingTextColor": "#3e9690",
"title": "Introduction: inovation for crisis",
"coverImage": "https://www.country067.com/wp-content/uploads/sites/28/2017/07/logoImage_4.jpg",
"descriptionUrl": "This is an option attribute. If not null this chapter will probably has no sections",
"sections": [
{
"id": 1,
"title": "Background",
"url": "http://api.example.com/chapter/1/section/1",
"projects": "null"
},
{
"id": 2,
"title": "Projects",
"url": null,
"projects": [
{
"id": 1,
"title": "Support to refugees",
"url": "http://api.example.com/chapter/1/project/1",
"coverImage": "https://example/wp-content/uploads/sites/28/2017/07/logoImage_4.jpg"
},
{
"id": 2,
"title": "title text",
"url": "http://api.example.com/chapter/1/project/2",
"coverImage": "https://example.com/wp-content/uploads/sites/28/2017/07/logoImage_4.jpg"
}
]
}
]
}
]
}
Using the decodable protocol, i created my models to map the response .
struct ChapterResult: Decodable {
let result: [Chapter]
}
struct Chapter: Decodable {
let id: Int
let heading: String
let headingTextColor: String
let title: String
let coverImage: String
let descriptionUrl: String
let sections: [Section]
}
struct Section: Decodable {
let id: Int
let title: String
let url: String?
let projects: [Project]?
}
struct Project: Decodable {
let id: Int
let title: String
let url: String
let coverImage: String
}
When calling the json decoder I do the following
let decoder = JSONDecoder()
let response = try decoder.decode(ChapterResult.self, from: data)
completion(.success(response.result))
which then results in the following error
failure(Optional(Error Domain=NSCocoaErrorDomain Code=4864 "Expected
to decode Array but found a string/data instead."
UserInfo={NSCodingPath=(
"CodingKeys(stringValue: \"result\", intValue: nil)",
"_JSONKey(stringValue: \"Index 0\", intValue: 0)",
"CodingKeys(stringValue: \"sections\", intValue: nil)",
"_JSONKey(stringValue: \"Index 0\", intValue: 0)",
"CodingKeys(stringValue: \"projects\", intValue: nil)"

Answer 1

It says result[0].sections[0].projects has a TypeMissMatch error.
So this "projects": "null" should be an array but it's string.

Answer 2

Read the error:
Expected to decode Array but found a string/data instead
In your JSON file projects have String or Array:
"projects": "null"
"projects": [
{
"id": 1
To fix the issue "null" should be null. If you can't edit JSON file you should write custom initializer.

Answer 3

see, Accroding to your struct
struct Section: Decodable {
let id: Int
let title: String
let url: String?
let projects: [Project]?
}
projects is a array of type project.
{
"id": 1,
"title": "Background",
"url": "http://api.example.com/chapter/1/section/1",
"projects": "null"
}
But at 0th index of sections, the value of projects key is "null" which is a string, so that's why you are getting an error.
Now read carefully your error it contains "Expected to decode Array but found a string/data instead."