Create a calculated field in my Entity

BIZ TMS Aurelius
1

I need to add a read-only field that does not exist in my database table.

I want the field to show up in my entity but not saved to the database. It's a calculated field only.

I tried something like this:
[Transient]
Property Onhand: Double Read GetOnhand;

I must be missing something with the [Column] or maybe it cannot be done. Not finding anything in the docs.

2

And then what happened? You can do that.
There is just no need for a Transient attribute, they apply only to fields.

3

Gave me an error that the column was undefined.

I deleted the project so I don't have the exact error message anymore.

Appears there needs to be a column defined. Did not know how to do that because then it says the column is missing in the database table.

4

There is no obligation for entity classes to have all members mapped. Please provide minimal detailed information - the full class declaration, the exact error message, etc. so we can provide better information about what might be happening.

5

Hi Wagner,

I'm having the same problem. See details below. FullName is not appearing in Swagger.. The only difference I can see from examples in the manual is that my Entity is linked to a table. I am using NexusDB.

Thanks,

Ken

[Entity]
[Table('Clients')]
[Id('FGUID', TIdGenerator.Guid)]
TClients = class
private
  [Column('"GUID"', [TColumnProp.Required])]
  FGUID: TGuid;
  [Column('LastName', [], 30)]
  FLastName: Nullable<string>;
  [Column('FirstName', [], 20)]
  FFirstName: Nullable<string>;
  function GetFullName: string;
public
  property GUID: TGuid read FGUID write FGUID;
  property LastName: Nullable<string> read FLastName write FLastName;
  property FirstName: Nullable<string> read FFirstName write FFirstName;
  property FullName: String read GetFullName;
end;

function TClients.GetFullName:String;
begin
  Result:=FirstName.Value + ' ' + LastName.Value;
end;
6

Hi @Randall_Ken,

You must explicitly tell XData you want the property to be in JSON:

https://doc.tmssoftware.com/biz/xdata/guide/json.html#aurelius-entities

i.e., add [XDataProperty] attribute to the new property.

7

Thanks. I have made the following change but still can't see it in Swagger. Anything else missing?

   [XDataProperty]
    property FullName: String read GetFullName;
8

Do you see it in JSON response/request?
Have you also added XData.Model.Attributes unit to the uses clause?

1 Like
9

I was not using unit Xdata.model.Attributes. It's working when I include it.

1 Like
10

I suggest that your next book is XData for Idiots :grinning:

11

Sorry, one more question. In the function is it possible to access a value from an associated entity that uses lazy loading?

12

I have resolved this. I have to put any function last in the select otherwise the other entities values are not available.

1 Like
13

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