The data types allowed to be transfered in DataSnap 2009 is limited to the dbExpress data types, but in DataSnap 2010 part of Delphi 2010 you are allowed to transfer any kind of object.
Let’s define the object we would like to transfer, class TCustomer
unit Customer;
interface
uses
DBXJSON, DBXJSONReflect, SysUtils;
type
TMaritalStatus = (msMarried, msEngaged, msEligible);
TCustomer = class
private
FName: string;
FAge: integer;
FMaritalStatus: TMaritalStatus;
public
property Name: string read FName write FName;
property Age: integer read FAge write FAge;
property MaritalStatus: TMaritalStatus read FMaritalStatus write FMaritalStatus;
function toString : string;override;
end;
Only objects that descend from TJSONObject are able to be transferred between client and server without any transformation in DataSnap 2010. If your object does not descend from TJSONObject, then you have to use the TJSONMarshal and TJSONUnMarshal classes to convert those objects. The example below shows how to make this conversion.
function CustomerToJSON(customer: TCustomer): TJSONValue;
var
m: TJSONMarshal;
begin
if Assigned(customer) then
begin
m := TJSONMarshal.Create(TJSONConverter.Create);
try
exit(m.Marshal(customer))
finally
m.Free;
end;
end
else
exit(TJSONNull.Create);
end;
function JSONToCustomer(json: TJSONValue): TCustomer;
var
unm: TJSONUnMarshal;
begin
if json is TJSONNull then
exit(nil);
unm := TJSONUnMarshal.Create;
try
exit(unm.Unmarshal(json) as TCustomer)
finally
unm.Free;
end;
end;
// protected
function TServerMethods.GetCustomer: TCustomer;
begin
Result := TCustomer.Create;
Result.Name := 'Pedro';
Result.Age := 30;
Result.MaritalStatus := msEligible;
end;
// public
function TServerMethods.GetJSONCustomer(): TJSONValue;
var
myCustomer: TCustomer;
begin
myCustomer := GetCustomer;
Result := CustomerToJSON(myCustomer);
myCustomer.Free;
end;
var
proxy: TServerMethodsClient;
myJSONCustomer: TCustomer;
begin
try
proxy := TServerMethodsClient.Create(SQLConnection1.DBXConnection);
myJSONCustomer := JSONToCustomer(proxy.myJSONCustomer);
Button1.Caption := myJSONCustomer.ToString;
myJSONCustomer.Free;
finally
SQLConnection1.CloneConnection;
proxy.Free;
end;
end;