For All Patch ThisRecord not working

[HansHeintz]

This used to work in my app

;;ForAll(
           MyCollection
               ;Patch(ThisRecord;{Test:"1"})
        ) 

Now it is just not doing anything anymore (no errors just ... nothing happens)

[RandyHayes]

@HansHeintz 

Your ForAll is backward - ForAll is a function that returns a table, not a For/Loop.

However, it appears that you are trying to change the Test column of all records in your collection.  If so, then utilize the following to do so:

UpdateIf(MyCollection, true, {Test:1})

I hope this is helpful for you.

[HansHeintz]

The ForAll function evaluates a formula for all the records in a table. The formula can calculate a value and/or perform actions, such as modifying data or working with a connection.

I guess I can forgive myself into thinking I can use ForAll as a For/Loop

Question remains why it was working and not anymore now.

Also why there are no error messages while I/m doing things backward.

I don't mind using UpdateIf in stead of ForAll but I am a bit worried that I have to find every instance of it in my app (finding code is not something Powerapps excels at) or otherwise my next update will leave all my users with problems.

I guess I should Use ClearCollect(MyCollection;ForAll(MyCollection..etc

Luckily I found this to search my code!

[RandyHayes · Accepted solution]

@HansHeintz 

The ForAll was designed as a table producing function.  It can do actions within it (depending on where you use the function).  However, most of the time it is used as a for/loop and causes bad performance in the app.  But, there are times that it has to be used as a loop.  It should be avoided if possible.  Whole different conversation.  But, suffice to say, there would not be an error message for it as PowerApps lets you use it either way.

Your initial formula would not do what you expect because you are just doing a Patch statement over and over depending on the amount of records in the MyCollection table. 

Patch is also a function that returns a record.  It will, in this case, not update your collection, it would simply be patching the record you provide it (ThisRecord) with another record ( {Test:1} ).  IN this context, patch will be returning a record only.  It is not given a datasource, only a record.  Patch is very intelligent depending on what you supply it.  If you supply a record as the source, it will only return a patched record.  So, your formula would do nothing because you are not capturing the result of the Patch.

I cannot imagine that that formula ever did anything because of what I mention above.  This is how that function works.  It doesn't patch or replace anything except the source and second records are patched together.

Searching for your formulas in PowerApps is a challenge and they should be centralized and minimized as much as possible to always avoid any duplication.  That said, it sounds like that is not the case for you and you have to look around for it.  So you'll need to rely on unpacking the app and viewing in VS or other editor.

The UpdateIf, based on your formula, will be more effective and efficient in this case.  So, I'd try to change in those places (and perhaps consider centralizing to a none duplicated formula the best you can).

Yes you could use :  ClearCollect(MyCollection; ForAll(MyCollection, Patch(ThisRecord, {Test:1})))

But that is a lot of processing for your app and will take it MUCH more time than : UpdateIf(MyCollection, true, {Test:1})

[v-jefferni]

Hi @HansHeintz ,

If the data source of the two functions is the same, it is not allowed to use ForAll with Patch/Update to update it:

Note the syntax of the Patch function, in your case it just merged the two records and finally create a new table, leave the collection unmodified:

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

Patch( Record1, Record2 [, …] )

• Record(s) - Required. At least two records that you want to merge. Records are processed in order from the beginning of the argument list to the end, with later property values overriding earlier ones.

https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/functions/function-patch#merge-records-...

Hope this helps.

Best regards,

Community Support Team _ Jeffer Ni
If this post helps, then please consider Accept it as the solution to help the other members find it.

[HansHeintz]

Looking into an earlier version of my app I found code had been changed after all so nothing changed with the forall, my bad.

ForAll does never change the collection it runs on it seems. 

I iterated throught all my uses of the function and nowhere else used it to change the collection itself but nowhere I use the return value of the function so I always thought it was meant to be a about changing what you throw at it.

[RandyHayes]

@HansHeintz 

Yes, it all depends on how you use the output of the ForAll to push it to your collection.  And, more importantly, how you specify the Patch statement.  In your case, you were patching two records...Patch would then return a result and do nothing else.  Since you were not capturing or using that, it was lost.

I believe it is important to view functions as functions that return a result.  Most all do.  Some do not.  Those that do not return results are meant to be in behavioral actions in your app.  Those that do, are meant to be used in non-behavioral actions (properties) and should be looked at that way.

A common misconception is :  ClearCollect(aCol, {"A val"});  Patch(aCol, {Value:"New val"}) 

The expectation many have is that this will change A val to New val.  The reality is, it does nothing.  The Collect function will create a table with one record with one column called Value and put the text "A Val" in it.

Patch will try to patch a table with a record...which will result in nothing and then Patch will return it, which will just be the original value, but it is not used...it is just discarded.

ClearCollect(aCol, "A val");  Update(aCol, First(aCol), {Value:"New val"}) on the other hand, uses Update - which will update a record in a table.  So, in this case, it will change the Value of the first record in the collection.

ClearCollect(aCol, "A val");  UpdateIf(aCol, Value="A val", {Value:"New val"}) likewise, will update the table record, in this case, the one that matches that value (criteria of Value="A val" is true).

In your case, you wanted to change all of the records in the collection, so using the UpdateIf(aCol, true, {Value:"New val"}) will update all records because the criteria will evaluate to true for every record...and thus it will update it.

So, the moral of the story is...use Update and UpdateIf to change your collection record values.  Otherwise you run into complexity.