Quick and Easy JSON Swift 4.1

It had always been a long and tedious task to parse JSON data in Swift. With Swift 4 it had become easy. And now with Swift 4.1 it has become even easier. The Decodable protocol is great.

Consider this JSON structure

[
    {
        id: 1;
        name: "Yogesh"
        image_url: "https://someurl.com/yogesh"
    },
    {
        id: 2;
        name: "Dan"
        image_url: "https://someurl.com/dan"
    },
    {
        id: 3;
        name: "Zack"
        image_url: "https://someurl.com/zack"
    }
]

In Swift 4 with a struct agreeing to Decodable we can parse out thing in the manner as
Note:- data used below is the data that has already been fetched from the server.

//Swift 4.0
struct Person: Decodable {
    let id: Int
    let name: String
    let image_url: String
}
let people = [Person]()
func parseJSON(data: Data){
    do {          
        let decoder = JSONDecoder()
        self.people = try decoder.decode([Person].self, from: data)
    } catch let error {
        print(error as? Any)
    }
}

The problem above is the image_url is in snake_case_name and we as Swift developers use camelCaseName and in Swift 4 we had to resolve this issue by doing stuff like below by using CodingKeys.
What CodingKeys enum lets you do is define custom keys for variables to parse out JSON.

//Swift 4.0
struct Person:Decodable {
    let id: Int
    let name: String
    let imageUrl: String
    //CodingKeys
    private enum CodingKeys: String, CodingKey {
        case imageUrl = "image_url"
        case id, name
    }
}

Above in Swift 4.0 we were able to parse out JSON with camelCase using CodingKeys. In Swift 4.1 it has become even more easier and quicker.

//Swift 4.1
struct Person: Decodable {
    let id: Int
    let name: String
    let imageUrl: String
}
let people = [Person]()
func parseJSON(data: Data){
    do {
        let decoder = JSONDecoder()
        decoder.keyDecodingStratergy = .convertFromSnakeCase
        self.people = try decoder.decode([Person].self, from: data)
    } catch let error {
        print(error as? Any)
    }
}

The decoder.keyDecodingStratergy = .convertFromSnakeCase is what is new here and it’s great.

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