How to create lookup fields using XDataClient?

BIZ TMS XData
1
Hi Wagner,

I'm having trouble creating lookup fields using XDataClient.

I have an Invoice object that references a Client object, ok.

I use the following command to return the list of Customers;

adsCustomer.Close;
adsCustomer.SetSourceList (FXDataClient.List <TCustomer> ('$ orderby = Name desc'));
adsCustomer.Open;

Then I use this command to return the Invoice list:

adsInvoice.Close;
adsInvoice.SetSourceList (FXDataClient.List <TInvoice> ('$ orderby = ID'));
adsInvoice.Open;

I can not do the Lookup, because each command above returns a different reference to the Custumer object.

How do i do the two above commands return the same reference to Client objects?
2

Indeed that's how it is now. You would have to manually manage to get the same instances of TCustomer in both lists. We're investigating a way to make the lookup work via ID of the instances instead of the references. But still not available.

3

Do you have any tips on how to do this management in an easier way?

4

You could use TObjectMap class declared in Aurelius.Engine.ObjectMap.pas unit. It handles the mechanism of keeping a single instance of an entity with same id, and has helper methods for that.

5
Wagner

Is there any example of how to do this management using the TObjectMap class?
6

Iterate through all Invoices and add its customers to object map:



for Invoice in Invoices do
  if not Map.IsIdMapped(Invoice.Customer) then 
    Map.Add(Invoice.Customer);

Do exactly the same for the customers returned in List<TCustomer>.
Then get the final list of customers using Map.GetList, to provide it to the dataset:


adsCustomer.Close;
adsCustomer.ObjectClass := TCustomer;
adsCustomer.SetSourceList (Map.GetList);
adsCustomer.Open;