I am wondering how the apps that allow a user to choose an item and, once the user has selected an item and checked out, give the retailer information about order that has been placed.

For example, say a takeaway has an iOS app and customer has chosen fish and chips and placed an order.

  1. How does the takeaway know an order has been placed? If it's TCP IP then I guess we need to start a server on the takeaway's computer? Is that right?

  2. How can modify the menu without making any changes in app from developer side?

I am looking for an answer about how things work in real world. Once I have the idea then developing it is a piece of cake.

  • The takeaway has an app on their computer which pops up when an order is placed. Commented Jun 23, 2020 at 14:16

2 Answers 2


I am wondering how does the retailer apps works which allows user to choose an item and once user have selected & checkout, the retailer get information about order been placed.

Typically the app posts the selection to a server. The buzz words you need to know to study this are Shopping Cart and E-Commerce. Many frameworks exist that would allow Fish & Chips takeaway to add their menu and pictures to their existing code. TCP/IP is just one of many technologies at work here (I'm assuming no one uses UDP for this but could be wrong).

2) how can add /remove/modify menu without making any changes in app from developer side?

Same way we've added our respective question and answer to softwareengineering.stackexchange.com. Code and content are separated. Everything we typed here doesn't end up in someones source code. It just becomes data. The source code doesn't care about the contents of the data. It just needs to know how to find it and display it. That means the content (menu, pictures) can be added long after they're done writing the code. The app can download the latest content the same as a web browser would do.

  • thanks for info. So basically to built an complete app I need to have 3 modules. first will be running on client/customer side through which they can place an order. Second will be server( remote location possibly my desktop) which receives request from client . And third app will be running on shopper's mobile which get notification from server about client order and sending info back to client. Am I right? I assume this is how just-eat app works?
    – samprat
    Commented Jan 19, 2017 at 2:55
  • @samprat Yes, sounds right Commented Jun 23, 2020 at 14:17

In your specific example, the data for the menu would be stored on the server somewhere. When the app wants to display the menu, rather than being concerned with the actual content, it would contain logic to display an arbitrary number of menu items in a specified way.

Your code would only need to know about the general structure of a 'Menu Item' (a price, an image, a description) etc.

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