How do I use SwiftUI with JSONDecoder for a Base64 string?

To use SwiftUI with JSONDecoder for a Base64 string, you'll need to perform a few steps. First, decode the Base64 string into Data, then use JSONDecoder to decode that Data into your desired Swift struct or class. Here's a breakdown:

1. Create a Decodable Struct or Class:

- Define a Swift struct or class that conforms to the Decodable protocol. This will represent the structure of your JSON data.

- Example:

struct MyData: Decodable {
  let name: String
  let age: Int
}

2. Decode the Base64 String:

- Convert the Base64 string to Data using Data(base64Encoded:). Handle potential errors if the string is not a valid Base64 string.

3. Use JSONDecoder to Decode the Data:

- Create an instance of JSONDecoder and use its decode(_:from:) method to decode the Data into your Decodable type.

4. Example Code:

import SwiftUI

struct ContentView: View {
  @State private var decodedData: MyData? = nil
  let base64String = "eyJuYW1lIjoiSm9obiBEb2UiLCJhZ2UiOjMwfQ==" // Example Base64 string

  var body: some View {
    VStack {
      if let data = decodedData {
        Text("Name: \(data.name)")
        Text("Age: \(data.age)")
      } else {
        Text("Decoding...")
      }
    }
    .onAppear(perform: decodeBase64String)
  }

  func decodeBase64String() {
    guard let base64Data = Data(base64Encoded: base64String) else {
      print("Invalid Base64 string")
      return
    }

    let decoder = JSONDecoder()
    do {
      decodedData = try decoder.decode(MyData.self, from: base64Data)
    } catch {
      print("Error decoding JSON: \(error)")
    }
  }
}

struct MyData: Decodable {
  let name: String
  let age: Int
}

5. Explanation:

- The ContentView uses @State to hold the decoded data. The onAppear modifier triggers the decodeBase64String function when the view appears.

- The decodeBase64String function first converts the Base64 string to Data. Then, it uses JSONDecoder to decode the Data into a MyData struct. Any errors during decoding are caught and printed to the console.

- The view displays the decoded data or a "Decoding..." message while the decoding is in progress.

This approach allows you to seamlessly integrate Base64 encoded JSON data into your SwiftUI applications by leveraging the power of JSONDecoder and Swift's data handling capabilities.

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