Summary

A short description of how to make something that functions like a WHILE loop in Power Apps using a button and a hidden toggle.

Reading Time: 3 minutes

Picture: One Infinite Loop, Ignacio Sanz, CC BY-SA 2.0, via Wikimedia Commons and Flickr

The Problem: Power Apps only has ForAll Loops

When I was creating a demo Power App to fetch and display Dad Jokes, one of the challenges I faced was to fit the joke text inside a speech bubble graphic. The speech bubble was expandable, but only within limits, so I needed to keep fetching jokes and checking the length of their text until I found one short enough to fit inside the bubble design.

Power apps editor screenshot with the text 'Too long'

After clicking the button: the app enters the loop and the text changes to ‘Too long’

However, looping in Power Apps turned out to be tricky. Unbelievably, I discovered there is only one kind of loop in Power Apps: ForAll, which is used for looping over tables and collections. Power Apps really doesn’t have any other kind of loops, or even GoTos in the coding it makes available.

Making a While Loop in Power Apps

However, after much research, trial and error, I found a way to do this with just the loop (More Dad jokes) button and a hidden toggle:

Hidden Toggle ‘While’ Loop:

More Dad jokes (loop) button:
  1. Sets varLoop to false
  2. Fetches joke
  3. Tests loop condition
  4. If loop is needed, sets varLoop to true
Toggle default:

Toggle default property is set to varLoop

Toggle onCheck:

Toggle onCheck property calls the function:
Select(more Dad jokes button)

Settings for the working WHILE loop with a Toggle

Here are the settings that worked:

Screen1.OnVisible

Power Apps Editor Screenshot: Screen1.OnVisible

When the app screen first loads, it sets the maximum joke length variable and loads the first joke by making an automated call to the ‘More Dad Jokes’ button


 
This is the code that goes in Screen1.OnVisible:
Set(MaxJokeLength, 160);
Select(FetchJokeButton)

The Loop Toggle

The loopToggle control is added inside the FrameContainer. Its Default property is set to varLoop and its Visible property is set to Off so it stays hidden from view except as an outline when it is selected for editing:

Screenshot showing the Deafult nd Visible properties of the loop Toggle control

The Toggle value will turn on and off depending on the value of varLoop

The loopToggle’s OnCheck property is set to Select(FetchJokeButton):

Power apps editor screenshot showing the loop Toggle OnCheck value of Select(FetchJokeButton)

When the loop Toggle is switched on, it performs an automated ‘click’ on the ‘More Dad Jokes’ button

The ‘More Dad Jokes’ Button

Finally, this is the code in the OnSelect property of the ‘More Dad Jokes’ button:
Set(varLoop, false);
ClearCollect(dadJokesCollection, DadJokes.FetchARandomDadJokeJson("application/json"));
If ((Len(First(dadJokesCollection).joke) > MaxJokeLength), Set(varLoop, true));

Clicking the ‘More Dad Jokes’ button, whether manually or by automation, resets the toggle back to Off, clears the collection, fetches a new joke and adds it to the collection (of one!), tests whether the joke is too long, and if it is, it switches the toggle back on, which restarts the loop by ‘clicking’ the button again:

Screenshot of the Power Apps editor showing the OnSelect property of the 'More Dad Jokes' button

Am I imagining things, or is this like a modern, event driven version of a GOTO?

See more detail about this app and how the While loop works in it here…

The working result:

After removing the test code and re-testing the app, the first joke seemed very appropriate:

Power Apps editor screenshot with the first joke in testing

“Remember, the best angle to approach a problem from is the ‘try’ angle”

(One Infinite Loop, Ignacio Sanz, CC BY-SA 2.0, via Wikimedia Commons and Flickr)

Using a Toggle to make a While Loop in Power Apps / Annabel Treshansky's Blog by blogadmin is licensed under a Creative Commons Attribution CC BY 3.0

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