Swift: Networking: Simple Request

by Annett Schwarze | 2025-06-29

Performing network communication in Swift is enabled using URLSession. A very simple request can be implemented with the asynchronous method `data(from: URL)` using just a couple of code lines.

For easy testing the Python package FastAPI provides a very simple and quick means. That way handling network requests can be tested in the simulator while the server can be started on the developer computer.

Preparing a FastAPI Server

There are two script files needed. One to prepare the Python environment and another which contains the FastAPI app. Disclaimer: This is not production ready code, so don't use it as such.

Setup script `minisrv_venv.sh`:

        
#!/bin/sh
if [ -d ./venv ]; then
    source ./venv/bin/activate
else
    python3 -m venv ./venv
    source ./venv/bin/activate
    python3 -m pip install fastapi[standard]
fi
fastapi run minisrv.py
deactivate
    

FastAPI Python script `minisrv.py`:

        
from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"result": "hi"}
    

Running the FastAPI server

To run the FastAPI server open a Terminal in the directory with these two script files.

Run the following command:

        
% sh ./minisrv_venv.sh
    

Press Ctrl-C to stop the FastAPI server when you don't need it any more or you want to restart it.

Performing the Network Request in Swift

To fetch the data, simply call `data(from: URL)` like shown in this function:

        
   private func sendRequest() {
        Task {
            do {
                guard let url = URL(string: "http://localhost:8000/") else { return }
                let (data, resp) = try await URLSession.shared.data(from: url)
                if let httpResp = resp as? HTTPURLResponse {
                    self.responseStatus = "\(httpResp.statusCode)"
                    if httpResp.statusCode != 200 {
                        self.responseInfo = "Error: Expected 200"
                        return
                    }
                }
                guard let string = String(data: data, encoding: .utf8) else { return }
                self.response = string
                self.responseInfo = "OK"
                self.errorInfo = "-"
            } catch {
                self.response = "-"
                self.responseStatus = "-"
                self.responseInfo = "-"
                self.errorInfo = "\(error.localizedDescription)"
            }
        }
    }
    

The full source code with the complete SwiftUI view is shown below:

        
import SwiftUI

struct SimpleRequestView: View {
    @State private var response: String = "-"
    @State private var responseStatus: String = "-"
    @State private var responseInfo: String = "-"
    @State private var errorInfo: String = "-"

    var body: some View {
        VStack {
            Text("Simple Request")
                .font(.largeTitle)

            Form {
                Button(action: {
                    sendRequest()
                }, label: {
                    Label("Send", systemImage: "paperplane")
                })
                LabeledContent("Response", value: response)
                LabeledContent("Response Status", value: responseStatus)
                LabeledContent("Response Info", value: responseInfo)
                LabeledContent("Error Info", value: errorInfo)
            }
        }
    }

    private func sendRequest() {
        Task {
            do {
                guard let url = URL(string: "http://localhost:8000/") else { return }
                let (data, resp) = try await URLSession.shared.data(from: url)
                if let httpResp = resp as? HTTPURLResponse {
                    self.responseStatus = "\(httpResp.statusCode)"
                    if httpResp.statusCode != 200 {
                        self.responseInfo = "Error: Expected 200"
                        return
                    }
                }
                guard let string = String(data: data, encoding: .utf8) else { return }
                self.response = string
                self.responseInfo = "OK"
                self.errorInfo = "-"
            } catch {
                self.response = "-"
                self.responseStatus = "-"
                self.responseInfo = "-"
                self.errorInfo = "\(error.localizedDescription)"
            }
        }
    }
}

#Preview {
    SimpleRequestView()
}