Friday, 24 April 2020

Power Apps Snack: Don't repeat yourself

Case
I have some pieces of code in my Power App that I use for several buttons, but I don't want to create multiple copies of that code. Is there a way to create a method or function with custom code that I can call from various buttons?
Power Apps and custom functions











Solution
No, Power Apps does not support methods or functions like real programming languages. However you can use the SELECT function. This function allows you to execute code from other objects on your screen, but only objects that have an OnSelect event.

Example 1: basics
For this example add two buttons to the screen: Button1 and Button2. In the OnSelect of Button1 add a simple Notify expression:
Notify(
    "Hello",
    NotificationType.Success,
    1000
)
Notify in OnSelect of Button1













In the OnSelect of Button2 add the Select expression:
Select(Button1)
Select in OnSelect of Button2













The Result
Now hit the play button to see the preview of your app. Then click both buttons and see the Notify showing for both buttons. You can even make Button1 invisible if you don't want to execute that code by it self, but only via other buttons.
Testing simple Select solution




















Example 2: parameters
By adding variables to the game you can even have some parameters for your new 'function'. Now change the OnSelect code of Button2 to:
UpdateContext({myParam: "Joost"});
Select(Button1)

And then add a third (and optional a fourth) button with the following OnSelect code:
UpdateContext({myParam: "Mark"});
Select(Button1)

Then change the OnSelect code of Button1 to:
Notify(
    "Hello " & myParam,
    NotificationType.Success,
    1000
)
And make Button1 invisible by setting the Visible property to false.

The Result
Now hit the play button again to see the preview of your changes. Click both visible buttons and see the Notify that now shows a different name for both buttons.
Testing Select with 'parameter'




















Conclusion
In this post you learned how NOT to repeat yourself with the Select function in Power Apps. Perhaps not the same features as in JavaScript, C# or any other language, but very useful to keep your code more clean. By hiding the buttons and giving them a descriptive, function-like name they could act like real programming functions.

An other great trick is to use the WITH function which is explained in an other post.


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