React Native Http Interceptor

Question

Like most applications, I'm writing an application that requires a lot of similar logic in the http response/requests handlers. For instance, I have to always check for refresh tokens and save them to the AsyncStorage, or always set the headers to my AuthService headers, or even check for 404 to route to the same 404 error page.

I'm a big fan of the http interceptor in Angular; where you can define and register an http interceptor to (lack of a better term) intercept all http traffic and then run the combined, common logic.

I have 2 main questions:

1. Since in React Native, we define these independent components, should we not be extracting common http logic in the first place in order to preserve the re-usability of the component?
2. If we don't want to duplicate code, is there a way in React Native (first) or Objective-C/Swift (second) to intercept http traffic and provide handlers for the requests?

Answer 1

Have you considered axios if you are trying to intercept only xhr? I am using axios interceptors - https://www.npmjs.com/package/axios and so far it seems to work.

Here is the sample code

import axios from 'axios';
import promise from 'promise';

// Add a request interceptor 
var axiosInstance = axios.create();

axiosInstance.interceptors.request.use(function (config) {
  // Do something before request is sent 
  //If the header does not contain the token and the url not public, redirect to login  
  var accessToken = getAccessTokenFromCookies();

  //if token is found add it to the header
  if (accessToken) {
    if (config.method !== 'OPTIONS') {
          config.headers.authorization = accessToken;
        }
  }
  return config;
}, function (error) {
   // Do something with request error 
   return promise.reject(error);
});

export default axiosInstance;

and then import this axiosInstance where ever you want to make xhr calls

Answer 2

I'm not sure if I'm understanding this question correctly, or if your looking for more magic, but it sounds like you just want a wrapper to the XMLHttpRequest (or fetch API). Wrap it in a class or a function and you can do whatever you want, whenever you want. Here's an example of an xhr wrapped in a promise:

function request(url, method = "GET") {
  const xhr = new XMLHttpRequest();

  // Do whatever you want to the xhr... add headers etc

  return new Promise((res, rej) => {
    xhr.open(method, url);
    xhr.onload = () => {
      // Do whatever you want on load...
      if (xhr.status !== 200) {
        return rej("Upload failed. Response code:" + xhr.status);
      }
      return res(xhr.responseText);
    };
    xhr.send();
  });
}

Then you can just use that whenever you want to do HTTP calls...

request("http://blah.com")
  .then(data => console.log(`got data: ${data}`))
  .catch(e => console.error(`error: ${e}`));