How can I parse a JSON string in swift?

Question

In my swift application, I am getting a JSON string from my server side and I am storing it using: let response = String(data: data!, encoding: .utf8)

The string contains and array of dictionaries. It looks like this:

[{"class":"Math","classToken":"SSC000000zctal","teacherName":"Last, First","room":"001","grade":"A+"},{"class":"MUSIC","classToken":"SSC000000zcY2Y","teacherName":"Last,First","room":"002","grade":"A+"}]

Is there a way for me to convert this to an actual array of dictionaries in my swift code?

take a look here you will find what you need stackoverflow.com/questions/25621120/… — belal medhat
– belal medhat, Commented Jan 29, 2022 at 23:21
Good. Now take the full response and convert it into a minimal valid representation. For example, the fact that there are 20 (vs an example of say, 2) items in the JSON array is largely irrelevant when determining the mapping structure. — user2864740
– user2864740, Commented Jan 29, 2022 at 23:36

Mr.SwiftOak · Accepted Answer · 2022-01-29 23:53:20Z

0

Here is how you can decode your response:

typealias YourDecodedObject = [ClassObject]

struct ClassObject: Codable {
    let welcomeClass: String?
    let classToken: String?
    let teacherName: String?
    let room: String?
    let grade: String?
    
    enum CodingKeys: String, CodingKey {
        case welcomeClass = "class"
        case classToken, teacherName, room, grade
    }
}

func decodeResponseFrom(data: Data?) {
    if let data = data {
        do {
            let decodedObject = try JSONDecoder().decode(YourDecodedObject.self, from: data)
        } catch {
            print("could not decode ❌")
        }
    }
}

answered Jan 29, 2022 at 23:53

Mr.SwiftOak

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3 Comments

Rohan Mittal Over a year ago

Thanks for writing this code. I still have two questions: 1. What is the purpose of welcomeClass? 2. What is the use of type alias in this?

Mr.SwiftOak Over a year ago

When decoding some response from server, we sometimes use CodingKeys, so that keywords in JSON object are not in collision with keywords that Swift uses during compiling. In example your JSON response includes "class" keyword in dictionary, since class cannot be property name (because class is used to create a class) we specify in Codingkeys, that JSON property named "class" would be decoded into properry with some other name - e.g. welcomeClass

Mr.SwiftOak Over a year ago

2) typealias is basically just placeholder name. We say that an array of [ClassObject] will be called YourDecodedObject . Then we use the YourDecodedObject to specify that we want to decode an array of [ClassObject] from server response

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