Service operations and excluding properties

BIZ TMS XData
1

Hi, I have some questions about using service operations and excluding properties.

The following class is used (from Hands-on: Delphi Web Services with TMS XData).

type
 [JsonInclude(TInclusionMode.NonDefault)] // added later
 TWorkoutItem = class
  private
    // Note: XData only looks at the private variables not property
    FStarting: TDateTime;
    FEnding: TDateTime;
    FDuration: Integer;
    FDistance: Integer;
    FInstructor: String;
    FTitle: String;
    FTotalOutput: Integer;
    FAvgWatts: Integer;
    FAvgResistance: Double;
    FAvgCadence: Integer;
    FAvgSpeed: Double;
    FCalories: Integer;

  public
    property Starting: TDateTime read FStarting write FStarting;
    property Ending: TDateTime   read FEnding write FEnding;
    property Duration: Integer read FDuration write FDuration;
    property Distance: Integer read FDistance write FDistance;
    property Instructor: String read FInstructor write FInstructor;
    property Title: String read FTitle write FTitle;
    property TotalOutput: Integer read FTotalOutput write FTotalOutput;
    property AvgWatts: Integer read FAvgWatts write FAvgWatts;
    property AvgResistance: Double read FAvgResistance write FAvgResistance;
    property AvgCadence: Integer read FAvgCadence write FAvgCadence;
    property AvgSpeed: Double read FAvgSpeed write FAvgSpeed;
    property Calories: Integer read FCalories write FCalories;

  end;

//

The dataset gets data from a service operation.

 XDataWebClient1.RawInvoke('IWorkoutService.List', [],
   procedure(Response: TXDataClientResponse)
   begin
     XDataWebDataset1.Close;
     XDataWebDataset1.SetJsonData(TJSObject(Response.Result)['value']);
     XDataWebDataset1.Open;
   end
 );

//

  1. How can I get the changes from XDataWebDataset as class object so I can send them to XData server via a service?
  2. Does [JsonInclude(TInclusionMode.NonDefault)] only send the properties which are changed?
2

Is there a reason you are using a service and not the standard CRUD endpoints? Makes life easy when using TXDataWebDataset.

3

I would like to have more control over the operation.

4

You can use GetPendingUpdates which will bring you a TResolveInfoArray value.

It only send properties in JSON if the value of the property is different from the default value for the type - for example, 0 for numeric values, empty string for strings, False for booleans. It won't include such values in JSON.

5

This would mean I have to filter out which fields are changed. Is my assumption correct?

In TAureliusDataset there is event DatasetObjectUpdate which returns AObject.

Does something similar exists in XDataWebDataSet and can only changed fields returned to LItem ?

LItem: TWorkoutItem;
begin
LService := FClient.Service;

//
LService.Update( LItem );

6

Yes and now.
Yes: such information is not directly available, to know which fields are changed, you need to implement it yourself somehow.
No: why would you need that?

Correct, there is no information about the changed fields in that event.

No, but you won't need the changed fields. Just send the whole modified object to the server.

7

No: why would you need that?

Only the modified fields of the table should be updated with the query in the service. When sending only modified fields (and values) the query could be flexible created.

Als I would like to prevent unnecessary data traffic.

No, but you won't need the changed fields. Just send the whole modified object to the server.

Does this mean XData server updates all fields (not only the modified)?

8

No. But it checks it server-side.

XData Aurelius automatic CRUD endpoints actually publishes a PATCH method where you can send only the modified properties in JSON, but that is not usually used in REST APIs and is not used anyway in neither TAureliusDataset/TXDataClient not TXDataWebDataset/TXDataWebClient combinations.

9

Thank you for the explanation.

10

Hi Wagner,
for this Attribute: '[JsonInclude(TInclusionMode.NonDefault)]`,
there is a way for setting the same effect (only filled properties n Json) at runtime?
Sometimes I need the complete Json, and sometimes, for example in queries, I need only the "essential" Json for performances, expecially when there are a lot of properties, but only few of them assigned.
(When your direct access to Postgres, Firebird, Mysql? :grinning:)
Thanks in advance!

11

Unfortunately no. You can create two classes for that, maybe.

We have seen low demand for this so it got lower priority in our (big) todo list.

12

Firebird would be very welcome :slight_smile:

13

Why? What's wrong with what you currently have?

14

Nothing - it works well. Just less code to manage. So don't worry about moving it up the list :wink:

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