Consuming Web Services in iOS

In-lecture exercise

Update the name property in the ViewModel class to match your first name (all lowercase, no spaces).

Implement the execute method of the struct HTTPRequestHandler to handle GET requests. To test your implementation run the app in the simulator or on device then click the 🔁 icon.

Solution

Your finished method should look something like this:

func execute(callback: @escaping (Result<Any>) -> Void) {
    guard let url = URL(string: path) else {
        callback(.failure(RequestError.invalidURL))
        return
    }

    var request = URLRequest(url: url)
    request.httpMethod = method.rawValue

    if let headers = headers {
        for (key, value) in headers {
            request.addValue(value, forHTTPHeaderField: key)
        }
    }

    if let body = body {
        do {
            request.httpBody = try JSONEncoder().encode(body as? ColorData)
        } catch (let e) {
            callback(.failure(e))
        }
    }

    let task = URLSession.shared.dataTask(with: request) { data, response, error in
        if let error = error {
            callback(.failure(error))
            return
        }

        guard let response = response as? HTTPURLResponse else {
            callback(.failure(RequestError.noResponse))
            return
        }

        guard response.statusCode < 400 else {
            callback(.failure(RequestError.httpResponse(response.statusCode)))
            return
        }

        guard let data = data else {
            callback(.failure(RequestError.noData))
            return
        }

        if let str = String(data: data, encoding: .utf8) {
            print("Received response: \(str)")
        }

        do {
            let colorData = try JSONDecoder().decode(ColorData.self, from: data)
            callback(.success(colorData))
        }
        catch {
            callback(.failure(RequestError.decoderFailure))
        }
    }
    task.resume()
}

Post-lecture exercise

Build upon your execute function to handle PUT requests as well. You can see what the post takes in as arguments in the ViewModel class under the setColor method. You will need to add header values to and serialize the body data for URLRequest.

To test your implementation, run your app in simulator or on device and select a color from the color picker. The color you picked should appear under your name in the companion web app.

Create a pull request with this updated code for review and feedback.