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Mario · Guest

Hi all!

I am trying to build an application which will access in future more than
one DB server.
I started now with Interbase and I have a question before going further.

I thought to use the Sigleton model for doing this and I don't know if this
is the best solution.
I have a connection class where some common methods are implemented and some
abstract methods are defined.
In the child class I have the abstract methods implemented.

I thought I should do this because of the fact that SQL statements differ
from server to server (sometimes)
and in the future I can build the next class(es) (Microsoft SQL Server e.g.)
without having to modify anything else in my app.
Is this a good aproach?!?!
I am using the Delphis DBExpress for doing this.
Is there any example available on the web how can this be or has been done?

Thanks for any opinion and help!
Mario

--------------------------------------------------------
{the main connection class}
TMDDBAbstractFactory = class
protected
MD_SHOW_EXCEPTIONS: Boolean;

MD_SQLConnection: TSQLConnection;
MD_SQLGeneralQuery: TSQLQuery;
public
constructor Create;
destructor Destroy; override;
{abstract widgets contructors}
//connects to a given database
//and returns True if the connection was successfull
function Connect2Database(DatabaseName: String) : Boolean; virtual;
abstract;
//creates a table in the database
//the TableFields is formated as FieldName||FieldType
//the FieldType will include also the constraints and all other
definitions
function CreateTable(TableName: String; TableFields: TStringList) :
Boolean; virtual; abstract;
//returns all records from the given table
//the result is true if the query can be executed
//and the dataset contains all the records in the table
function GetAllRecords(var ASimpleDataSet: TSimpleDataSet; TableName:
String;
SelectedFields: String = '*') : Boolean;
//returns the number of records in a given table as integer
function GetRecordCount(TableName: String) : Integer;
//inserts a record in the given table
function InsertRecordInTable(TableName: String; TableFields,
TableValues: Variant) : Boolean;
//deletes a record from the given table
function DeleteRecordFromTable(TableName: String; ConditionFields,
ConditionValues: Variant) : Boolean;
end;

--------------------------------------------------------
{Interbase connection class}
TMDDBInterbaseFactory = class(TMDDBAbstractFactory)
public
constructor Create;
{concrete widgets constructors}
function Connect2Database(DatabaseName: String) : Boolean; override;
function CreateTable(TableName: String;
TableFields: TStringList) : Boolean; override;
end;

Joanna Carter (TeamB) · Guest

Mario wrote:

Mario · Guest

Just started reading...
Thanks!

Mario

"Joanna Carter (TeamB)" <joannac (AT) btinternetXX (DOT) com> wrote