mORMot Open Source

lagodny

Member

Registered: 2015-01-28

Posts: 50

Nested classes in Cross-Platform

Are there any plans to add support for nested classes in the Cross-Platform?

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,661

Website

Re: Nested classes in Cross-Platform

What do you call "nested classes"?
Joined ORM fields?

The idea with cross-platform clients is that you rather define DTO objects, not directly access complex ORM classes.

There is no plan to support it yet.
But any input is welcome!

lagodny

Member

Registered: 2015-01-28

Posts: 50

Re: Nested classes in Cross-Platform

I meant something like this:

  TMyParams = class
  private
    FP1: Boolean;
  published
    property P1: Boolean read FP1 write FP1;
  end;

  TMyRec = class(TSQLRecord)
  private
    FTitle: string;
    FParams: TMyParams;
  public
    destructor Destroy; override; // to destroy FParams
    class function NewInstance: TObject {$IFDEF AUTOREFCOUNT} unsafe {$ENDIF}; override; // need override NewInstance to create FParams (constructor TObjects isn't virtual)
  published
    property Title: string read FTitle write FTitle;
    property Params: TMyParams read FParams write FParams;
  end;

const
  cStoreClassName = True;
...
  r := TMyRec.Create;
  try
    r.Title := 'Hello';
    r.Params.P1 := True;
    aJSON := ObjectToJSON(r, cStoreClassName);
  finally
    r.Free;
  end;

  r := TMyRec(JSONToNewObject(aJSON))

I made some tests.
1. The function ObjectToJSON have parameter StoreClassName: boolean=false. So we don't have ClassName to create nested classes in SynCrossPlatformREST by default. Is it possible to make it customizable?
2. The code works on Win32. On Android there is a problem with
function JSONToNewObject(const JSON: string):  pointer;
should be
function JSONToNewObject(const JSON: string): TObject;

And a question. Is it possible to somehow teach the mORMotWrappers to generate nested classes? Or should I put them in the template? Or I should use nested records and arrays?

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,661

Website

Re: Nested classes in Cross-Platform

Nested records and arrays, defined as DTO is the right way to do it.

For your Params field, I think you could just use a variant for TMyRec definition, which will create a JSON variant.

lagodny

Member

Registered: 2015-01-28

Posts: 50

Re: Nested classes in Cross-Platform

Thanks, ab