mORMot Open Source

turrican

Member

From: Barcelona

Registered: 2015-06-05

Posts: 94

Website

Help about table relationship

Hi,

I have read documentation and I cannot find a example using an easy way to do "Has Many" relationship.

I need to implement an aproach to "Lazy loading" of nested records relation in a table.

My aproach is the next, but I don't know if is a best way to do this :

uses
  System.SysUtils,
  mormot,
  mORMotSQLite3,
  mORMotDB,
  System.Contnrs,
  synsqlite3static;

type

  TUser = class(TSQLRecord)
    private
      fname: UTF8String;
      fgroupid: TID;
    published
      property IDGroup: TID read fgroupid write fgroupid;
      property Name: UTF8String read fname write fname;
  end;

  TGroupe = class(TSQLRecord)
    private
      fclient: TSQLRestServerDB;
      fname: UTF8String;
      fusers: TObjectList;
    public
      function GetUsers(aClient: TSQLRestServerDB): TObjectList;
      function AddUser(aClient: TSQLRestServerDB; aUser: TUser): TID;
    published
      property Name: UTF8String read fname write fname;
  end;

function TGroupe.GetUsers(aClient: TSQLRestServerDB): TObjectList;
begin
  if Assigned(fusers) then fusers.Free;
  fusers:=aClient.RetrieveList(TUser, 'IDGroup=?', [ID]);
  Result:=fusers;
end;

function TGroupe.AddUser(aClient: TSQLRestServerDB; aUser: TUser): TID;
begin
  aUser.IDGroup:=ID;
  Result:=aClient.AddOrUpdate(aUser);
end;

var
  fSQLContext: TSQLRestServerDB;
  x: Integer;
  user: Pointer;
  group: TGroupe;
  groupid: TID;
begin
  try
    { TODO -oUser -cConsole Main : Insert code here }
    fSQLContext:=TSQLRestServerDB.Create(TSQLModel.Create([TUser, TGroupe], 'root'),'prueba.db3');
    fSQLContext.CreateMissingTables;
    Writeln('Create Group');
    group:=TGroupe.Create;
    group.Name:='Test Group';
    Writeln('Storing group');
    groupid:=fSQLContext.Add(group, True);
    Writeln('Adding users to group');
    for x := 0 to 100 do
    begin
      user:=TUser.Create;
      TUser(user).Name:='Name ' + x.ToString;
      writeln('Added user with id : ' + Int64(group.AddUser(fSQLContext,User)).ToString);
      TUser(user).Free;
    end;
    Writeln('Users added, freeing group');
    group.Free;
    Writeln('Create group again and retrieve users');
    group:=TGroupe.Create;
    fSQLContext.Retrieve(groupid,group);
    begin
      for user in group.GetUsers(fSQLContext) do
      begin
        writeln(TUser(user).Name);
      end;
    end;
    Readln;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.

Help me!

Bo

Member

From: Melbourne

Registered: 2016-07-04

Posts: 57

Website

Re: Help about table relationship

Hi turrican,

Have you figured out yet?