Making API Calls to Fetch Weather Data in Swift

In this unit, we will delve into the practical aspect of working with Weather APIs in Swift. We will learn how to make API calls to fetch weather data and handle the responses effectively.

Understanding HTTP Requests and Responses

HTTP stands for Hypertext Transfer Protocol. It is a protocol used for transferring data over the internet. An HTTP request is made to a server from a client, and the server responds to the client with an HTTP response.

There are several types of HTTP requests, but the one we are interested in for fetching data from a Weather API is the GET request. A GET request is used to request data from a specified resource.

Making GET Requests in Swift

In Swift, we can make GET requests using the URLSession class. Here's a basic example of how to make a GET request to a Weather API:

let url = URL(string: "https://api.weatherapi.com/v1/current.json?key=YOUR_API_KEY&q=London")!

let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
    if let error = error {
        print("Error: \(error)")
    } else if let data = data {
        // handle data here
    }
}

task.resume()

In this example, we first create a URL object with the URL of the Weather API. We then create a data task with this URL, which will send a GET request to the API when resumed.

Handling API Responses and Errors

The data task's closure is called when the GET request is complete. It has three parameters: data, response, and error. If an error occurred during the request, the error parameter will contain an Error object, and data and response will be nil. If the request was successful, data will contain the data returned by the server, response will contain a URLResponse object with information about the server's response, and error will be nil.

To handle the data returned by the server, we can use the JSONDecoder class in Swift to decode the data into a model object. Here's an example:

let decoder = JSONDecoder()
if let weatherData = try? decoder.decode(WeatherData.self, from: data) {
    // use weatherData here
}

In this example, we first create a JSONDecoder object. We then call its decode(_:from:) method, passing in the type of the model object we want to decode the data into and the data itself. If the method call is successful, it returns a model object with the decoded data.

By the end of this unit, you should have a solid understanding of how to make API calls in Swift and handle the responses. This knowledge will be crucial for fetching and handling weather data in your weather application.