Tersus: Demo Stage 4 – Refresh: Publish-subscribe to automatically refresh the list upon any update

Demo Stage 4 – Refresh: Publish-subscribe to automatically refresh the list upon any updateDate: Jun 7, 2020

In the Repository Explorer:

Create a new package 'Publish-Subscribe' (right-click on the top level package 'ShoppingList').
Create an action 'Subscribe to Shopping List Changes' (right-click on the 'Publish-Subscribe' package).
Drag 'Subscribe to Shopping List Changes' into the 'ShoppingList/<Desktop View>/Items/Init' action.

Model 'Subscribe to Shopping List Changes' to get notification on any change in the list:

Drag into it 'Subscribe' (from the 'Miscellaneous' section of the palette).
Create a text constant "Any" and connect it to the '<Channel>' trigger of 'Subscribe'.
Model the behavior upon a change notification:
- Zoom into ' ShoppingList/<Desktop View>/Items/Header Row/Refresh Group/Refresh'.
- Select 'Get Current Page Number', 'Go to Page' and the flow between them. Press Copy.
- Zoom back to 'Subscribe to Shopping List Changes' , then into 'Subscribe' and then into '<On Message>'.
- Press Paste (Reuse):

Create a 'Publish Change' action that will notify of any change in the list:

Go back to the 'Publish-Subscribe' package in the Repository Explorer and create an action 'Publish Change' (right-click on the 'Publish-Subscribe' package).
Open 'Publish Change' (double-click from the Repository Explorer) and add to it a trigger 'Record'.
Drag 'Publish Change' into the 3 places in the model where the database is updated (all 3 are inside 'Header Row/Action Header Group'):
1. Into the 'New/Enter Details/Footer/Save/Save New' service. Link the 'Output' exit of 'Perform Action' to the trigger of 'Publish Change'.
2. Into the 'Update/Update Details/Footer/Save/Save Update' service. Link the 'Output' exit of 'Perform Action' to the trigger of 'Publish Change'.
3. Into the 'Delete/Delete from DB' service. Link the 'Output' exit of 'Perform Action' to the trigger of 'Publish Change'.

Model 'Publish Change' itself as follows (see comments below the screenshot):

Now: Drag from the 'Dates' section of the palette.
Any: Re-use the constant from the 'Subscribe to Shopping List Changes' action.
Item: Re-use the database record from the package 'ShoppingList/Desktop/Items/Wizard/Database'.
Message: Re-use 'Common/Templates/Notification/Message'.
Publish: Drag from the 'Miscellaneous' section of the palette.

If you now start the application, any change you make to the list from your PC will immediately show on your iPhone/Android (if you don't have a smartphone, open two browsers, one to make a change and the other to see the automatic refresh of the list).Note that the updater experiences two refreshes of the table upon any update – one due to the built-in refresh process in each of the buttons, and one due to the subscription to updates. To overcome this problem, users should ignore updates made by themselves. This issue will be handled in Stage 9.Download Model: Stage 4 (version 2.1.9) Next: Adding item statusesSee Also:

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