Sending string from JSON data to variable outside of the function

I am attempting to take a string from JSON data and set it to a variable. My problem is that the variable shows as empty. I am using JSONDecoder to retrieve the JSON data and setting the string to a variable outside of the function. I then want to use that variable inside of another function

When I print the variable it still shows up as blank even after the function has loaded. Within the function the string appears correctly.

Code:

var filmTitle = ""

override func viewDidLoad() {
    super.viewDidLoad()


loadFilms()
print(self.filmTitle) //Prints as an empty string

}

func loadFilms() {
    
    let id = filmId
    let apiKey = "97a0d64910120cbeae9df9cb675ad235"
    let url = URL(string: "https://api.themoviedb.org/3/movie/\(id)?api_key=\(apiKey)&language=en-US")
    let request = URLRequest(
        url: url! as URL,
        cachePolicy: URLRequest.CachePolicy.reloadIgnoringLocalCacheData,
        timeoutInterval: 10 )
    
    let session = URLSession (
        configuration: URLSessionConfiguration.default,
        delegate: nil,
        delegateQueue: OperationQueue.main
    )
    
    let task = session.dataTask(with: request, completionHandler: { (dataOrNil, response, error) in
        if let data = dataOrNil {
            do { let details = try! JSONDecoder().decode(Details.self, from: data)
        self.filmTitle = details.title
        print(self.filmTitle) //string prints correctly

                        }
                    }
                })
    
    
    task.resume()
    
}

What am I missing to correctly set the string to the variable?

The solution to this problem was to reload the collection view that the array was being sent to within the decoder function after the data was set to the array.