Loading a value from another table

BIZ TMS Aurelius
1

I have read about associations but not sure if that is what I am looking as it seems quite weighty.


I have 2 objects (simplified here)

TLocation = class
  ID: Integer;
  Name: string;
  Address: string;
end;

TEvent = class
  ID: Integer;
  Name: Integer;
  Date: TDateTime;
  LocationId: Integer;
end;

and I either want to add another field to TEvent or do a descendant which includes the linked TLocation.Name.

so either

TEvent = class
  ID: Integer;
  Name: Integer;
  Date: TDateTime;
  LocationId: Integer;
  LocatioName: string;
end;

or

TEventEx = class(TEvent)
  LocationName: String;
end;

What would be the easiest way and/or correct way to implement this in Aurelius?

Thanks.


2

The correct way is to create a property like this in TEvent:



TEvent = class
  Location: TLocation;

It's the TLocation object associated with the TEvent. That way you always have all Location data accessible from Event:


Event.Location.Id;
Event.Location.Name;
3

is there an example of using this with the TXDataWebDataSet?


The music xdata-web example, doesn't map the Album.Artist this way.

Also, how do you select the sub fields for a grid?

Thanks
4
My definition is

    [Association([TAssociationProp.Lazy],CascadeTypeAllButRemove)]
    [JoinColumn('LOCATIONID', [])]
    FLocation: TBuzzLocation;

and when I run the app I get

Project VCL_Buzz_XServer.exe raised exception class EAssertionFailed with message 'Field/property is not a Proxy<T> type (C:\DC\TMS Aurelius\source\core\Aurelius.Mapping.Explorer.pas, line 2341)'.

5

You have added [TAssociationProp.Lazy] flag to it indicating you want that association to be lazy-loaded, but you didn't declare the field as a proxy. You must either remove TAssociationProp.Lazy or declare FLocation as Proxy<TBuzzLocation> (recommended). Here is more info about it and sub properties:


http://www.tmssoftware.biz/business/aurelius/doc/web/lazy-loading_associations.html
http://www.tmssoftware.biz/business/aurelius/doc/web/sub-property_fields.html
6

Is the Invoice code used in the documentation available as a demo?

7

No but in the Music Library demo there is a similar entity with lazy-loaded list.