• Check API document at the movie DB

URl

• First, we need to convert a URL String to a URL instance.

URL(string: String)  // Creates a URL instance from the provided string.

• Second, create expected task on provided URL instance, like downloading from or uploading data to specific URL

URLSession.shared.dataTask(with: , completed)

• Finally, call resume() function to initialize tasks

PROTIP: Keep in mind to deal with the async problem using the @escape keyword

JSON decoder

To decode data in JSON format to specific formats like arrays, structs, etc.

1. Make sure the targeted data type, especially if it is a customized type, is codable

struct Title: Codable{
 ....
}

2. Create JSON decoder

let decoder = JSONDecoder()

3. Decode from json data to specific type

do{
                // Here we decode data in json format into [Title] array
                let results = try JSONDecoder().decode(TrendingTitleResponse.self, from: data)
                completion(.success(results.results))
            }
            catch{
                completion(.failure(error))
            }

---

/// Get trending movies, tvs, popular movies, etc from TMDB's API
class APICaller{
    static let shared = APICaller()
    /// Fetch data from given API then decode the data from JSON to [Title] array
    /// To deal with async problem, we use @escaping to enable the closure to outlive current scope to keep trying to connect to the network until get expected data
    /// We also use method resume() to initialize the data tasks
    func getTrendingMovies(completion:@escaping (Result<[Title],Error>) -> Void){
        guard let url = URL(string: "\(Constants.baseURL)/3/trending/movie/day?api_key=\(Constants.API_KEY)") else{return}
        // URLSession coordinates a group of tasks for downloading data from and uploading data to endpoints indicated by URLs
        // URLSession.shared is a convenient shared singleton session that gives you a reasonable default behavior for creating task
        let task = URLSession.shared.dataTask(with: URLRequest(url: url)){data, _, error in
            guard let data = data, error == nil else{
                return
            }
            
            do{
                //                let results = try JSONSerialization.jsonObject(with: data,options: .fragmentsAllowed)
                
                // Decode from json data to specific type
                // Here we decode data in json format into [Title] array
                let results = try JSONDecoder().decode(TrendingTitleResponse.self, from: data)
                completion(.success(results.results))
            }
            catch{
                completion(.failure(error))
            }
        }
        
        // Newly-initialized tasks begin in a suspended state, so you need to call this method to start the task.
        task.resume()
    }