TP2WDAConnection

TP2WDAConnection will connect to your Data Abstract server and log into your Data Abstract server’s LoginService.

Additionally, TP2WDAConnection can do other things for you — such as create a RemObjects ClientChannel or RemObjects Message.

Important note

Unless you use a LoginService with custom methods, there is probably no need to handle the following events:

1. OnCreateService. Because TP2WDAConnection expects a LoginService by name, not by reference.
2. OnConnectionStringNeeded. You don't need this unless your LoginService demands more credentials than a username and a password.

When in doubt, set the below properties and ignore the above events.

Properties

property	description
LoginServiceName	Specifies the name of the service to call if authentication with the server is needed, typically this is LoginService.
MessageType	RemObjects sends (and receives) messages that get serialized (and deserialized). This property specifies the structure of the messages. Possible values are mtAuto or mtBin or mtJSON. When set to mtAuto, TP2WDAConnection will try and auto-detect the message type from the URL to the server.
Password	Your password for the login service.
URL	Specifies the URL to the server, for example: http://localhost:7099/bin
Username	Your username for the login service.

Methods

method	description
CreateChannel	Channels facilitate communication between client and server, or between different services. There is probably no need to create a channel manually, but if you ever need to do it, this method returns a new channel for you over the HTTP protocol.
CreateMessage	Messages are sent over channels between client and server, or between different services. There is probably no need to create a message manually, but if you ever need to do it, this method creates a new (binary or JSON) message for you. See also: TP2WDAConnection.MessageType.

Events

event	description
OnCreateService	Most of the time, you will specify a LoginService by name and be done with it. In most cases there is no need to add any custom methods to the LoginService. However, if your LoginService does have custom methods you would need to call from Delphi, this event is where to create it. See also: OnCreateService.
OnConnectionStringNeeded	If your LoginService needs a username/password combination only, there is no need to respond to OnConnectionStringNeeded. However, if your LoginService needs a custom login string to authenticate, this is where to provide it. See also: OnConnectionStringNeeded.

OnCreateService

Here is an example of a LoginService with one or more custom methods. You would need to define a so-called "external class" and then create and return an instance of this class as a response to TP2WDAConnection.OnCreateService:

type
  TMyLoginService = class external name 'MyProject.LoginService'(TBaseLoginService)
    procedure MyCustomMethod(onSuccess: TOnSuccess; onFailure: TOnFailure);
  end;

procedure TForm1.ConnectionCreateService(Sender: TObject; const Channel: TROClientChannel; const Msg: TROMessage; var Service: TROService);
begin
  Service := TMyLoginService.new(Channel, Msg, Connection.LoginServiceName);
end;  

Should you need access to your custom LoginService (to call a custom method on it, for example), this is how to get it:

var
  MyLoginService: TMyLoginService;
begin
  MyLoginService := Connection.LoginService as TMyLoginService;
  ...
end;

OnConnectionStringNeeded

Your LoginService probably needs a username/password combination only. However, if your LoginService needs a custom login string to authenticate, here is an example how to provide it:

procedure TForm1.ConnectionStringNeeded(Sender: TObject; var ConnectionString: string);
begin
  ConnectionString := ConnectionString + ';Domain=DASamples;Schema=Simple';
end;