How to pass arguments into a function with completion swift

Question

I'm new to swift and am wondering how I can pass arguments into a function when that function has a completion. I tried just passing in a variable String but that did not work. Here is my class for handling an api request. This is where i need to pass the contents to so that it can add it to a search field and return the results.

public class API {
    
    func apiRequest(search: String, completion: @escaping (Result) -> ()) {
        
        //URL
        var query = search.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)
        let url = URL(string: "https://calorieninjas.p.rapidapi.com/v1/nutrition?query=" + query!)
        
        //URL REQUEST
        var request = URLRequest(url: url!, cachePolicy: .useProtocolCachePolicy, timeoutInterval: 10.0)
        
        //Specify header
        let headers = [
            "x-rapidapi-key": "3be44a36b7msh4d4738910c1ca4dp1c2825jsn96bcc44c2b19",
            "x-rapidapi-host": "calorieninjas.p.rapidapi.com"
        ]
        
        request.httpMethod="GET"
        request.allHTTPHeaderFields = headers
        
        //Get the URLSession
        let session = URLSession.shared
        
        //Create data task
        let dataTask = session.dataTask(with: request) { (data, response, error) in
            
            let result = try? JSONDecoder().decode(Result.self, from: data!)
            print(result)
            DispatchQueue.main.async {
                completion(result!)
            }
             
            
        }
        
        //Fire off data task
        dataTask.resume()
        
    }
}

This is my content view code where I am trying to pass in the contents of a text box into this function so that i can get the result back from the api:

struct ContentView: View {
    
    @State var result = Result()
    @State private var searchItem: String = ""
    
    var body: some View {
        ZStack(alignment: .top) {
            Rectangle()
                .fill(Color.myPurple)
                .ignoresSafeArea(.all)
            VStack {
                TextField("Enter food", text: $searchItem)
                    .background(Color.white)
                    .padding()
                    .textFieldStyle(RoundedBorderTextFieldStyle())
                
                SearchButton()
                    .padding(.top)
                    .onTapGesture {
                        API().apiRequest { (result) in //IDEALLY I WOULD LIKE TO PASS IN THE CONTENTS OF THE TEXT BOX HERE INTO apiRequest
                            self.result = result
                        }
                    }
                
            }
        }
    }
}

I'm sure the solution is simple I am just not used to the syntax and such of swift quite yet any help with this is much appreciated.

Answer 1

Your function 'apiRequest' has 2 parameters:

1. search: String (this parameter expects a String)
2. completion: @escaping (Result) -> ()

So when you call this method, you will pass these 2 parameters as well, like this:

.onTapGesture {
    API().apiRequest(search: "String you want to pass", completion: { (result) in
        self.result = result
    })
 }

Learn about closures, as this completion parameter is also a type of closure (escaping closure).