Explore key concepts of networking in Swift with questions on URLSession, REST APIs, and related techniques. Enhance your understanding of API requests, JSON parsing, and asynchronous handling in Swift app development.
Which URLSession task type is best suited for downloading a large file asynchronously in Swift?
Explanation: URLSessionDownloadTask is designed to handle downloading large files efficiently by writing data directly to a temporary file. URLSessionDataTask is mainly for fetching smaller pieces of data that fit in memory. URLSessionUploadTask is specialized for uploading data rather than downloading. URLSessionStreamTask is intended for bidirectional streaming, making it unsuitable for downloading large files.
Which HTTP method should be specified in a URLRequest for retrieving data from a REST API in Swift?
Explanation: The GET method is used for retrieving information from a server without modifying any data, which is the standard for data-fetching operations. POST is typically used to send data or create resources, not just retrieve information. SEND is not a valid HTTP method. PUT is used for updating or replacing resources on the server.
Which Swift structure can be used to decode JSON data received from a REST API when using Codable?
Explanation: Decodable is used in Swift to decode JSON data into custom structures or classes, enabling you to parse API responses efficiently. Encodable is meant for encoding data to JSON but not for decoding. Serializable is not a Swift protocol related to JSON parsing. Descriptive is not relevant in this context.
What parameter type is typically used in the completion handler of a URLSessionDataTask in Swift?
Explanation: A URLSessionDataTask completion handler receives three parameters: Data?, URLResponse?, and Error?, which represent the response data, metadata, and potential error. The other options list types not used together in this context, such as String, Int, and Float or collections like Array and Dictionary.
Which class is used to configure background downloads with URLSession in Swift?
Explanation: URLSessionConfiguration is utilized to set up various session behaviors, including background downloads, by specifying its 'background' option. SessionManager is not a standard class for configuration in this context. BackgroundSession and DownloadManager are not built-in Swift classes or configuration tools.
Which method allows you to set an HTTP header value for a URLRequest in Swift?
Explanation: The setValue(_:forHTTPHeaderField:) method directly sets a value for a specific HTTP header in a URLRequest. The other options, such as addHTTPHeader(_:), setHeader(_:withValue:), and updateHeaderField(_:value:), are not valid methods in the URLRequest API.
What is the typical HTTP status code to check for a successful network response when using URLSession in Swift?
Explanation: Status code 200 indicates a successful response from the server, meaning the request was handled correctly. 404 signals the resource wasn't found, 500 points to a server error, and 301 signifies a resource has permanently moved, none of which indicate success.
Why is it important to execute URLSession network requests on a background thread in Swift?
Explanation: Running network requests on a background thread ensures the app interface remains responsive and prevents freezing or lag. Faster download speeds are not a direct result of threading. Lowering battery usage and storing data locally are unrelated to the need for background network execution.
When making a POST request to submit JSON data using URLSession, which property should you set on the URLRequest?
Explanation: The httpBody property of URLRequest holds the data sent with the request, such as JSON for POST requests. bodyStream is an alternative for streaming data but is less common for simple JSON. requestBody and dataSource are not valid URLRequest properties.
In the URLSession completion handler, which parameter should you check first to safely handle errors?
Explanation: You should first check the error parameter, as its presence indicates network failures or issues with the request. The data and response parameters might be nil or incomplete if an error occurred. info is not a parameter provided in the completion handler.