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Saving new record with Patch function

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Posted on by SimonMeadows

171

I have a function for generating a customer code that checks all existing codes and increments the highest by 1 to create a new one.

This is the formula:

Patch(newCust,ThisItem,{company: newCompany.Text});
Clear(codeCount);
ForAll(
 Search(
 '[LV1_DB].[Customer]',
 Left(First(newCust).company,4),
 "AccountCode"
 ),
 Collect(
 codeCount,
 {
 Value: Value(
 Right(
 AccountCode,
 2
 )
 )
 }
 )
);
ForAll(
 Search(
 '[dbo].[tblCust]',
 Left(First(newCust).company,4),
 "Customer_code"
 ),
 Collect(
 codeCount,
 {
 Value: Value(
 Right(
 Customer_code,
 2
 )
 )
 }
 )
);

Patch(
 newCust,
 ThisItem,
 {
 code: Concatenate(
 Upper(
 Left(ThisItem.company,4)
 ),
 Text(
 Max(
 codeCount,
 Value
 )+1,
 "[$-en-US]00"
 )
 )
 }
)

If I have both sections of the formula run on the OnChanged event of the newCompany field it creates a new record in my newCust collection.

If I split the formula as above, put the first part on the OnChanged event of the newCompany field and the second part on a button it patches the current record as it should.

This formula is running within the context of a Gallery on a collection that would normally only have one record.

I am not using the Default() function so why would it be creating new records?

Categories:

Building Power Apps

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SimonMeadows 171 on at

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Ok, so im half answering my own question but it would be good to know why it makes a difference.

If I change all references from 'ThisItem' to 'First(newCust)' the formula operates as expected.

Why, in the gallery, if im in the context of the first record in the newCust collection would there be any difference between the reference to 'ThisItem' and and the reference to 'First(newCust)'?
Shouldn't they be the same record reference?

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Verified answer

Meneghino 6,949 on at

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Hi @SimonMeadows
I have to admit I did not work through all the details of your post, however here is what I learned about the Defaults(MySource) function and its combined use with Patch().

1) The Defaults function will put out a new call to the data source each time it is used, so if you are patching multiple records this impacts app performance negatively (for example within a ForAll loop). In order to avoid this, I normally create a collection like this:
ClearCollect(MySourceDefault, Defaults(MySource))
I normally do this as part of the OnStart of the first screen. Then I can use Patch(MySource, First(MySourceDefault), etc. etc.) instead of the usual Patch(MySource, Defaults(MySource), etc. etc.)

2) Actually, what follows from 1 above is that you do not even need to call the Defaults function at all unless you really have some explicit default values. The following for example works with Azure SQL DB to create a new record where the table's primary key is ID
Patch(MySource, {ID: Blank()}, etc. etc.)
I am not sure this helps, but if for some reason ThisItem returns a record which has Blank() as the value of the primary key field(s), then a new record will be created.

Hope this helps.

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