Show only new data from http get requests

Hello,
I’ve made an Ionic angular app that reads and writes data from/to a mysql database.

In the section I’m working now there is a list of orders: i get the list with a http get request from my backend and then I show it looping the response with *ngFor. Every 60 seconds i do a new http request for updating the orders list.
Everything works just fine.

But how can I show an alert with the newest values only?

The practical example would be a printer connected to my app that prints every new order from the backend, a restaurant for example, that prints automatically the new orders

Thank you :slight_smile:

I would expect this to be murderous on battery life, so eventually you may wish to look into a push notification solution.

The first solution that comes to mind would be to have some sort of “recorded” field in each order, and a counter in the frontend app indicating “I’ve displayed everything recorded before 2021-01-02 03:04:05”. Each request could include their “seen everything before” timestamp in the request, and the server could then respond only with orders recorded after then.

Yeah that’s how I managed to "fix it temporarily " but I was looking for a more elegant way :slight_smile: thank you!

I would think an alert with changes is a side effect you could establish adding the tap operator to the rxjs pipe, and then use the timestamp to filter out/count/give any info you like to give.

Tap I think is a typical side-effect operator - you do need to use sparingly imho

thank you, i’ll try this solution too.

You could also try out something like a ‘subscription’ if the framework and / or SDK / library you are using support such API. That way only recent records could be fetched from the DB.

This convention of solicitations and reactions empowers you see this page in your browser.HTTP expects information to be moved starting with one point then onto the next over the network.or if your program consequently demands something from the worker, another association GET demands are one sort of HTTP technique a customer can call.