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Passing Auth Token from Native to Portal

A common scenario that a developer might run into is having a web experience tailored for the current logged in user. Another scenario might be having a log-in screen be a Portal so it can easily be designed and updated across Android and iOS. In both of these scenarios, a developer would need to account for handling auth tokens between native and web code. Below are a few examples of how to solve these problems.

Passing From Native to Web​

When showing a Portal after a user has logged in, there are a few different ways to pass user auth tokens to a Portal.

  • Providing a value to the initialContext argument of the Portal initializer.
  • Using the @ionic/portals to publish a message to the web app with the current auth tokens.
  • Using a custom plugin to send data back and forth from native and web.

Setting the Initial Context​

The easiest way to set the Portal's auth tokens is to set the initial context of the portal. The initial context will allow you to pass data that can be read almost immediately in the Portal.

let userPage = Portal(
    name: "user_page",
    initialContext: [
        "route": "/user",
        "auth": /* Auth Data */
    ]
)

Then, in the entry point to your web application, you can use getInitialContext() to read the data passed in and act on it.

import { getInitialContext } from "@ionic/portals";

type MyPortalContext = { route: string; auth: any };
const auth = getInitialContext<MyPortalContext>()?.value?.auth;
// rest of the web app...

Using a Custom Plugin​

Another solution you can do is to create a custom Plugin to handle passing data to and from native and web. This is the solution we used in the example E-commerce Application since it scales nicely and allows more than just authentication data be passed to and from the layers.

For information on how to build your own Portal APIs, see our how-to guide.

How to Pass Data From Web to Native​

In some cases, login information changes in the web layer and you want to save the new auth credentials in the native layer. There are several ways of doing that similar to the previous methods.

Using the Pub/Sub Functions in @ionic/portals​

One of the functions of the built-in portals module is to publish/subscribe to events. In this example, you could create a login topic and call publish as shown below.

import { publish } from "@ionic/portals";

const login = () => {
  // Login code...

  const topic = "login";
  const newTokens =
    /* Values from Login */

  publish(topic, newTokens);
};

login();

To subscribe to the topic, call subcribe after loading the Portal.

let cancellable = PortalsPubSub.shared.subscribe(to: "login") { result in
    let auth = result.data
    // Rest of the native app...
}

For more information on how to communicate with a Portal web application, see our how to guide.

Using a Custom Plugin​

Similar to the previous section, by creating a custom plugin, you have complete control over how to communicate between web and native layers. It is possible to create a function such as MyPlugin.syncAuthAcrossWebAndNative() to handle managing auth tokens across web and native.

For information on how to build your own Portal APIs, see our how-to guide.

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