Get data from JSON, only if it is in array

Hi, I am trying to create a function that when passed a URL containing a JSON file and a list of names, it returns me some structure.

I have created (with help) the function that returns all the values of the JSON without problem, but I am having problems filtering them and only returning those that are in the array.

Code Block 
let urlString = "https://jsonplaceholder.typicode.com/users"
let arrayInput = ["Leanne Graham", 
"Nicholas Runolfsdottir V"]

This is what I use for the function that returns all data:

Code Block 
struct WelcomeElement: Codable {
    let name: String?
    let username: String?
    let email: String?
}
typealias Datos = [WelcomeElement]
class UserItems {
    var purchases = [WelcomeElement]()
    func loadData(urlString: String, completion: @escaping (Datos) -> Void) {
        let url = URL(string: urlString)!
        URLSession.shared.dataTask(with: url) { data, _, error in
            if let error = error as NSError?, error.domain == NSURLErrorDomain, error.code == NSURLErrorNotConnectedToInternet {
                print("Not connected")
            }
            do {
                let items = try JSONDecoder().decode([WelcomeElement].self, from: data!)
                self.purchases = items
                completion(items)
            } catch {
                print(error)
            }
        }.resume()
    }
}

And this is the function that I have created to return certain values but I get an error and I don't know if it is well handled.

Code Block 
class UserItems {
    var purchases = [WelcomeElement]()
    var purchases_new = [WelcomeElement]()
    func loadData(urlString: String, arrayInput: Array<String>, completion: @escaping (Datos) -> Void) {
        let url = URL(string: urlString)!
        URLSession.shared.dataTask(with: url) { data, _, error in
            if let error = error as NSError?, error.domain == NSURLErrorDomain, error.code == NSURLErrorNotConnectedToInternet {
                print("Not connected")
            }
            do {
                let items = try JSONDecoder().decode([WelcomeElement].self, from: data!)
                for position in 0...items.count-1 {
                    for a in arrayInput {
                        if a == items[position].name {
                            print(items[position])
                            self.purchases_new = items[position]  // Cannot assign value of type 'WelcomeElement' to type '[WelcomeElement]'
                        }
                    }
                }
                self.purchases_new = items
                completion(items)
            } catch {
                print(error)
            }
        }.resume()
    }
}

Surely there is a more efficient way to find the value of the array in the json but that was the only thing that occurred to me.

This function, I use it to create a table with the structure.

Any help is welcome, thank you!

Code Block 
self.purchases_new = items[position]  // Cannot assign value of type 'WelcomeElement' to type '[WelcomeElement]'

Code Block 
self.purchases_new.append(items[position])

Code Block 
                print("Not connected")
                return

Code Block 
                self.purchases_new = items

Code Block 
for position in 0...items.count-1 {
    for a in arrayInput {
        if a == items[position].name {
            purchases_new.append(items[position]) 
            break
        }
    }
}

Code Block 
purchases_new = items.filter() { arrayInput.contains($0.name)}