Using LookUp inside ForAll to check if value is in 2 separate collections.

[anon23u9412]

I am trying to see if a certain value of a field is present in 2 separate collections.

For instance below, The app would first check if English is present in Collection 2, then if Maths if in Collection 2 and so on.. 

Collection 1:

Item	Specialism
1	English
2	Maths
3	Geography
4	Computing

Collection 2:

Item	Specialism
1	History
2	Computing
3	Physics
4	Music

This is my current code:

ForAll(
    Collection1,
    If(
        IsBlank(
            LookUp(
                Collection2,
                Specialism.Id = ThisRecord.Specialism.Id
            )
        ),
        true,
        false
    )
);

After doing some digging I have found that using 'ThisRecord' within LookUp is probably the issue. Most people seem to solve this by adding 'As' (in my case: ForAll(Collection 1 As _____)...) however I can't seem to get this to work either. 

Any help would be greatly appreciated.

[RandyHayes]

@anon23u9412 

What are you using this for?  What is the output of your ForAll table being applied to?  

As you have it now, you will result in a table of records with a Value column that is true or false.

So what is the comparison being used for?

[cpadilla]

Hello!,

As per my understanding, you want to know if there are repeated records in different collections/tables, correct?

If so, let me suggest the following approach:

UpdateContext({col1: Table(
    {item:1, Specialism: "spanish"},
    {item:2, Specialism: "maths"},
    {item:3, Specialism: "geo"},
    {item:4, Specialism: "computing"}
)});
UpdateContext({col2: Table(
    {item:1, Specialism: "history"},
    {item:2, Specialism: "computing"},
    {item:3, Specialism: "physics"},
    {item:4, Specialism: "music"}
)});
ClearCollect(repeated, Blank());
ForAll(
    col1,
    With(
        {val: LookUp(
            col2 As col2,
            col2.Specialism = ThisRecord.Specialism,
            col2.Specialism
        ) },
        If(
            !IsBlank(val),
            Collect(repeated,val)
        )
    )
);

the output would be a collection called "repeated" with all the records present in collection 1 and collection 2, or empty if no records are repeated

let me know if this helps 

[RandyHayes]

@cpadilla 

The use of the ForAll is backwards.  ForAll is a function that creates a table of records, not a for loop.  

If you use it improperly, your performance and experience will suffer from it.

To do that formula you have properly, it would be:

With({col1: 
    Table(
      {item:1, Specialism: "spanish"},
      {item:2, Specialism: "maths"},
      {item:3, Specialism: "geo"},
      {item:4, Specialism: "computing"}
    ),
    col2: 
    Table(
      {item:1, Specialism: "history"},
      {item:2, Specialism: "computing"},
      {item:3, Specialism: "physics"},
      {item:4, Specialism: "music"}
    )
    },

    ClearCollect(repeated, 
        Filter(col1, Specialism in col2)
    )
)

A ForAll is not needed (especially as a for loop)

However my question to @anon23u9412 pertains to what is the result to be used for.  ForAll outputs a Table, so where is that needed?

If the desire was to have a Gallery show the list of duplicated items, then the Items property of the Gallery would be pretty much the same as the correct formula above.

And adapting to @anon23u9412 's provided data, it would be:

Filter(Collection1, Specialism in Collection2.Specialism)

All very simple...no collections or ForAll (correctly used or not) needed.

[anon23u9412]

Hi,

The application works like this (I abstracted quite a bit of the complexity in my original post)

--------------------------

I have a list of specialisms that a person can have (In a SharePoint list):

ID	User_ID	Specialism
1	example@example.com	Maths
2	example@example.com	Computing
3	example@example.com	English
4	anotherexample@example.com	Geography
5	anotherexample@example.com	Physics
6	anotherexample@example.com	ICT
...	...	...

In my application I get all specialisms for the current logged in user.

So if 'example@example.com' was logged in I would get the following into a into a collection 'Specialisms' an then into a gallery:

Specialism

Maths

Computing

English

The user can then add and remove specialisms from this collection using controls in the application (This part of the application works perfectly).

When getting the above specialisms into collection 'Specialisms' I also duplicate this collection into another called 'originalSpecialisms'.

When the user has made their changes to the list of Specialisms they click to submit their updated specialisms back into the database. Here I compare the updated 'Specialisms' collection with the 'originalSpecialisms' collection. 

If a specialism is present in both collections then I do not add it to the database as it is already present.

If a specialism is present in only 'Specialisms' then it needs to be added to the database.

If a specialism is present in only 'originalSpecialisms' then the user wishes to remove it so I will remove it from the database.

In reality I will have 2 ForAll loops, one for adding to and one for removing from the database. 

Instead of 'true' I will have the code to Patch the record and in the other ForAll loop I will have the code to Remove the row from the Sharepoint list instead of 'true'

[RandyHayes]

@anon23u9412 

So then the formula I mentioned to @cpadilla will provide what you need.

Filter(Collection1, Specialism in Collection2.Specialism)

Will give you a list of your items from the Collection1 that are already found in Collection2

However, it seems you want the values that are NOT in the other collection.

In which case the formula would change to:

Filter(Collection1, !(Specialism in Collection2.Specialism))

[anon23u9412]

That makes much more sense than the approach I was taking!

I am getting an error, though. 

My specialism field contains both an Id and a Value so I try to put:

Filter(SpecialismCollection, OriginalSpecialismCollection in SpecialismCollection.Specialism.Id)

and I get the error: "Name isn't valid. 'Id' isn't recognised"

If I remove the .Id I get the error: "Can't convert this data type. Powerapps can't convert this Table to a Record'

Thanks for your help with this.

[RandyHayes]

@anon23u9412 

Yes, that is not going to work for two reasons:

1) You are trying to use a table (OriginalSpecialismCollection) to compare with a dissimilar table.

2) You have a record in the record (a lookup), so it needs its value pulled out.

What is OriginalSpecialismCollection and how is it defined?

[anon23u9412]

When I populate the list of specialisms I create the collection SpecialismCollection  to store them and display them in the gallery whilst the users adds to and removes from the list and I also create OriginalSpecialismCollection which is populated and then left unchanged. I then compare the difference between these 2 collections when updating my data source.