Can someone explain this peculiar behavior of creating an entity with lookup value?

[MrNappa]

I got this error message when trying to create a new record that contained a lookup field. When investigating it further, I found the following.

My code was set up like:

// Create item
UpdateContext({ 
  reg: { 
    vdt_name: "test",
    vdt_date: Now()
  }
});

// [..] some other code

// add reference to item
UpdateContext({
  reg: Patch( reg, { vdt_refitem: LookUp( RefItems, RefItem=selected.RefItemId ) } )
});

// save the item
Patch( Registrations, Defaults( Registrations ), reg );

This gave me an error "Value must be an entity record" on the final patch to the data source.

However, when I changed it to the following:

// Create item
UpdateContext({ 
  reg: { 
    vdt_name: "test",
    vdt_date: Now(),
    // include the reference now
    vdt_refitem: LookUp( RefItems, RefItem=selected.RefItemId ) 
  }
});

// [..] some other code

// save the item
Patch( Registrations, Defaults( Registrations ), reg );

This code runs and works correctly.

I inspected the contents of the variable in both scenarios, and they both seem to contain all fields that I specified, including the lookup value. The only difference is that in the first instance, the lookup field reference is added later by doing a patch. What makes this not work?

[v-yutliu-msft]

Hi @MrNappa ,

That's a little strage...

Did you make other changes about variable reg?

Could you tell me Registrations table and RefItems table's structure?

I've made a test and found that the two ways to create variable will result the same data.

Here's my test:

UpdateContext({ 
  reg: { 
    vdt_name: "test",
    vdt_date: Now()
  }
});
UpdateContext({
  reg: Patch( reg, { vdt_refitem: {id:"aa"} } )
});

UpdateContext({ 
  reg1: { 
    vdt_name: "test",
    vdt_date: Now(),
    vdt_refitem: {id:"aa"}
  }
});

And the result:

Best regards,

[MrNappa]

Hi Phoebe,

The field is a simple Lookup field to another table. 

Also -- after some further testing, I it might have something to do with async behavior of the patch command?

If you look at the following test:

You can see that only the 2nd patch is 'problematic'. If I include the lookup field in the original UpdateContext, or if I Patch it with a cached value, the final patch seem to work correctly.
Update: Actually, when I comment out the 2nd patch line, the third patch also gives an error. So that was a false positive.