collection, forall: how process item based on property of previous item

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Posted on by HansHeintz

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Hi,

When showing an item of a collection in a gallery I want to only show a label if a text property of the item differs from the same property of the previous one.

I thought I
add a column: showlabel
do a forall and compare the text propery against a string variable: if different showlable:true else showlabel:false

if different also store the text property to the string variable for comparing the next item

and then set label visible property to showlabel in the end

Alas for some reason I cannot store anything into variable inside a forall. UpdateContext and Set are forbidden.

So how then?

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Building Power Apps

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v-yutliu-msft Microsoft Employee on at

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Hi @HansHeintz ,

Yes, it's not supported to use UpdateContext and Set function in ForAll function currently, because they could easily be used to hold variables that would be susceptible to this effect.

Here's a doc about ForAll function for your reference:

https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/functions/function-forall

Please modify your formula.

If you still have any problem, please show me your formulas.

This will help me understand better.

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HansHeintz 704 on at

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“would be susceptible to this effect”
What effect are you talking about?

I have no code to evaluate because i do not know how to approach this problem. That was my question.

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v-yutliu-msft Microsoft Employee on at

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Hi @HansHeintz ,

Inside ForAll function, you need to avoid ordering dependencies.

You could refer the doc that I listed for details.

To sum up, within PowerApps, UpdateContext function is not supported to used within the ForAll function.

I suggest you consider put he UpdateContext function outside the ForAll function.

For example,

UpdateContext({var:ForAll(.....)})

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