Two questions: Global CLR objects and Method chainig in VC++ 2005

Dear all
Hi

I am Saeed Amrollahi. I write C++ programs using VC++ 2005 CLR/CLI. I
have two problems:
1. How to declare/define and use global ref class objects? For example
for database connection/communication, I usually define a class called
DBBroker, When I used MFC, DBBrk wraped the Recordset/ODBC facilities
and now it wraps the ADO.Net facilities:

ref class DBBroker { // A wrapper class for all database manipulation
public:
DBBroker();
void Open();
bool IsOpen();
void SetQuery(const std::wstring&);
void SetUpdQuery(const std::wstring&);
void SetInsQuery(const std::wstring&);
void Close();
/*
* Load functions
*/
std::map<std::wstring, std::wstring> LoadSQLFilename();
// ...
/*
* Get functions
*/
int GetNextAvailInvestorId();
// ...
/*
* Update functions
*/
void UpdAccLogin();

/*
* Insert functions
*/
void InsIndividual();

~DBBroker();
private:
System::Data::OleDb::OleDbConnection^ Conn;
System::Data::OleDb::OleDbCommand^ Command;
System::Data::OleDb::OleDbDataAdapter^ Adapter;
};

Now I want to define one and only one global object:
DBBroker^ g_DBBrk = gcnew DBBroker();
At the moment, I have to define a DBBroker object for each form and
database operation and obviously, it is base practice.
2. As you know, If I have the following native C++ class:
class C {
public:
C& f();
C& g();
};

then, I can write the following code:
C c;
c.f().g();
How to use the method chaining inside a ref class:
public ref class SingleInvestorRegForm : public
System::Windows::Forms::Form
{
public:
SingleInvestorRegForm^ FillNationalityComboBox();
SingleInvestorRegForm^ FillSexComboBox();
};

FillNationalityComboBox()->FillSexComboBox(); // or something like
that

Thanks in advance,

Regards,
S. Amrollahi

Saeed Amrollahi wrote:
> Dear all
> Hi
>
> I am Saeed Amrollahi. I write C++ programs using VC++ 2005 CLR/CLI. I
> have two problems:
> 1. How to declare/define and use global ref class objects? For example
> for database connection/communication, I usually define a class called
> DBBroker, When I used MFC, DBBrk wraped the Recordset/ODBC facilities
> and now it wraps the ADO.Net facilities:
>
> ref class DBBroker { // A wrapper class for all database manipulation
> public:
> DBBroker();
> void Open();
> bool IsOpen();
> void SetQuery(const std::wstring&);
> void SetUpdQuery(const std::wstring&);
> void SetInsQuery(const std::wstring&);
> void Close();
> /*
> * Load functions
> */
> std::map<std::wstring, std::wstring> LoadSQLFilename();
> // ...
>                 /*
> * Get functions
> */
> int GetNextAvailInvestorId();
> // ...
> /*
> * Update functions
> */
> void UpdAccLogin();
>
> /*
> * Insert functions
> */
> void InsIndividual();
>
> ~DBBroker();
> private:
> System::Data::OleDb::OleDbConnection^ Conn;
> System::Data::OleDb::OleDbCommand^ Command;
> System::Data::OleDb::OleDbDataAdapter^ Adapter;
> };
>
> Now I want to define one and only one global object:
> DBBroker^ g_DBBrk = gcnew DBBroker();
> At the moment, I have to define a DBBroker object for each form and
> database operation and obviously, it is base practice.

How about using the singleton pattern?
(http://en.wikipedia.org/wiki/Singleton_pattern). With help of templates you
 can
transform a class into a singleton without touching their code (see
Alexandrescu's aproach in the loki library http://www.ddj.com/cpp/184401943)


> 2. As you know, If I have the following native C++ class:
> class C {
> public:
>   C& f();
>   C& g();
> };
>
> then, I can write the following code:
> C c;
> c.f().g();
> How to use the method chaining inside a ref class:
> public ref class SingleInvestorRegForm : public
> System::Windows::Forms::Form
> {
> public:
>    SingleInvestorRegForm^ FillNationalityComboBox();
>    SingleInvestorRegForm^ FillSexComboBox();
> };
>

> FillNationalityComboBox()->FillSexComboBox(); // or something like
> that
>

Yes, the sentence is correct.


--
Cholo Lennon
Bs.As.
ARG

On Apr 16, 12:54=A0am, "Cholo Lennon" <chololen...@hotmail.com> wrote:
> Saeed Amrollahi wrote: 
> 
> 
> 
> 
> 
>
> How about using the singleton pattern?
> (http://en.wikipedia.org/wiki/Singleton_pattern). With help of templates y=[/color
]
ou can
> transform a class into a singleton without touching their code (see
> Alexandrescu's aproach in the loki libraryhttp://www.ddj.com/cpp/184401943=[/color
]
)
>
>
>
>
> 
> 
> 
>
> Yes, the sentence is correct.
>
> --
> Cholo Lennon
> Bs.As.
> ARG- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -

Hi Cholo
Thank you. Your answer for second question was good. For the first
question:
my problem isn't single instance creation, Indeed I want to declare/
define a global ref object,
then using extern, I want to reuse such object in other translation
units:

// 1.h
public ref class DBBroker {
// ...
};

// main.cpp
// global definition
DBBroker^ DB =3D new DBBroker();

// 2.cpp
extern DBBroker^ DB;
// now use global DB

Thanks
- Saeed

Hi Saeed,

> Thank you. Your answer for second question was good. For the first
> question:
> my problem isn't single instance creation, Indeed I want to declare/
> define a global ref object,
> then using extern, I want to reuse such object in other translation
> units:
>
> // 1.h
> public ref class DBBroker {
>   // ...
> };
>
> // main.cpp
> // global definition
> DBBroker^ DB = new DBBroker();
>
> // 2.cpp
> extern DBBroker^ DB;

Define a static public ref class with a static public method which
returns your singleton.

--
SvenC

On 16 avr, 09:28, Saeed Amrollahi <s_amroll...@yahoo.com> wrote:

> my problem isn't single instance creation, Indeed I want to declare/
> define a global ref object,
> then using extern, I want to reuse such object in other translation
> units:

You can't declare global variable in .NET. The singleton is the right
solution (you should also use it in native C++, it is anyway a better
pattern, that a global "extern" object).
You could also make the DBBRoker class static : if you declare only
one instance of this class, there is no real reason to have it
instanciable...

Arnaud

> my problem isn't single instance creation, Indeed I want to declare/
> define a global ref object,
> then using extern, I want to reuse such object in other translation
> units:
>
> // 1.h
> public ref class DBBroker {
>   // ...
> };
>
> // main.cpp
> // global definition
> DBBroker^ DB = new DBBroker();
>
> // 2.cpp
> extern DBBroker^ DB;
> // now use global DB

This is correct, except ref class instances live on the managed heap, so use
gcnew instead of new.

>
> Thanks
>   - Saeed