Re: Operator= overloading [edited - bis] - C / C++ / MFC Discussion Boards

smartymanav28-Jun-05 21:02

28-Jun-05 21:02

i am using access datase linking by odbc....

is ado better???or it is possible to do so in odbs using access database

acually the thing is i am already using a database for retrieving data in a form in this same project....

i now want to use another table in the same database for retriving data in to another form

plz help or suggest a diff way

thanks

Re: a problem!!!!

toxcct29-Jun-05 0:15

toxcct

29-Jun-05 0:15

sorry, i don't know at all how to use access DB...

you should ask this in a separate thread...

(search also on codeproject && google ; there are certainly many useful articles on the subject)...

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Re: a problem!!!!

Cool Ju29-Jun-05 23:42

Cool Ju

29-Jun-05 23:42

Hi,

U can use CDaoDatabase and CDaoRecordset Classes to handle databases. U can directly open access(.mdb) databases and also thro odbc. These classes support both of them. U can also ADO. it is better than DAO. Refer MSDN for more details.

Bye
Cool Ju Cool | :cool:

Re: a problem!!!!

smartymanav28-Jun-05 20:57

smartymanav

28-Jun-05 20:57

thanks a lot
it solved my prob thanks again!!!

but can u tell me another thing

plz suggest me a medthod to permanently save the changes made during run time into a array of strings in vc++

i tried to use database but am unable as i am already using a database to get data into a form in the same project

do u know how to get data from multiple tables in the same project into diff forms...

thanks again

Re: a problem!!!!

Christian Graus28-Jun-05 20:37

Christian Graus

28-Jun-05 20:37

smartymanav wrote:
for ef ctr is 3 and still c1 is getiing a value like -85899346

Never define a variable anywhere without giving it a default value. Otherwise, this is what you get. I think the other response covers your more specific problem.

Christian Graus - Microsoft MVP - C++

Operator= overloading

Member 341989128-Jun-05 20:01

Member 3419891

28-Jun-05 20:01

How to get such a kind of operator= overloading that given a class instance we will be able to do this

class Test
{
int m_data[10][10];
public:
void operator=(int x);
};

Test tst;
tst(2,3) = 20; //and that 20 number will be put to m_data[2][3] ?

9ine

Re: Operator= overloading

Christian Graus28-Jun-05 20:06

Christian Graus

28-Jun-05 20:06

You can't, at least I don't think so.

Christian Graus - Microsoft MVP - C++

Re: Operator= overloading [edited - bis]

toxcct28-Jun-05 20:23

toxcct

28-Jun-05 20:23

i don't understand you're problem...

you want to overload the operator=() for your class Test ?

nop, it's not actually what you want. here, you need an operator=() that returns an int. right ?
but what you can't do is reaching the (2,3) cell in your array.
so, you have to overload the operator()()...

<font color=blue>class</font> Test {
    <font color=blue>int</font> m_data[10][10];
 
  <font color=blue>public</font>:
    Test();
    <font color=blue>virtual </font>~Test();
    <font color=blue>void operator</font>=(<font color=blue>int</font>);    <font color=green>// not needed anymore</font>
    <font color=blue>int</font>& <font color=blue>operator</font>()(<font color=blue>int</font> x, <font color=blue>int</font> y);
};
 
<font color=blue>int</font>& Test::<font color=blue>operator</font>()(<font color=blue>int</font> x, <font color=blue>int</font> y) {
    <font color=green>// Tests if the indexes are in the ranges...</font>
    <font color=blue>if</font> (x <  0) x =  0;
    <font color=blue>if</font> (y <  0) y =  0;
    <font color=blue>if</font> (x > 10) x = 10;
    <font color=blue>if</font> (y < 10) y = 10;
    <font color=green>// Reaches the value...</font>
    <font color=blue>int</font>& ri = m_data[x][y];
    <font color=blue>return</font> ri;
}

this way, when you do:

Test tst;
tst(2, 3) <font color=green>// equivalent to tst.operator()(2, 3)</font>
  = 20;   <font color=green>// will use the standard operator=() working on integers</font>
ASSERT(tst(2,3) == 20);
 
Test *pTst = &tst;   <font color=green>// Pointer to tst</font>
(*pTst)(2, 3) = 21;  <font color=green>// Changes via a pointer the value of tst(2, 3)</font>
ASSERT(tst(2,3) == 21);

cheers,

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Re: Operator= overloading

Cedric Moonen28-Jun-05 20:31

Cedric Moonen

28-Jun-05 20:31

It is not the = operator that you need to overload but rather the [] operator. But in your case you have two nestled [] operators so you will need to make use of an intermediate class (like RowTest).
Something like that:

<br />
class RowTest<br />
{<br />
int m_data[10];<br />
public:<br />
int& operator[](int x);<br />
};<br />
<br />
<br />
class Test<br />
{<br />
RowTest m_data[10];<br />
public:<br />
RowTest& operator[](int x);<br />
};<br />

Then, by overloading this operator you will be able to do this:

Test tst;<br />
tst[2][3] = 20;

But of course there is an extra class involved. The syntax is perhaps not correct because I don't play a lot with these kind of things.

Hope this helps

Re: Operator= overloading

toxcct28-Jun-05 20:33

toxcct

28-Jun-05 20:33

nop, not the operator[]() because it can get only once value between the [ ]...

prefer operator ()()...

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Re: Operator= overloading

Cedric Moonen28-Jun-05 20:37

Cedric Moonen

28-Jun-05 20:37

Yes, that's why you need to make use of an intermediate class... But ok, it may be a little bit too complicate. The other solutions were simplier Smile | :)

Re: Operator= overloading

Member 341989129-Jun-05 3:52

Member 3419891

29-Jun-05 3:52

I dont need extra class I'm going to check out of range x,y for m_data[x][y] in overloaded operator so I need that class will act as an array.
With simple array we can assign a value to it and read it:
int val;
val = m_data[x][y];
m_data[x][y] = val;

All this I want to be done by class

class Test
{
int m_data[10][10];

public:
int operator()(int x, int y);

};
int Test::operator()(int x, int y)
{
//check if x,y out of range
return m_data[y][x];
}

1. so we can read value by overloaded () operator
Test tst;
int val = tst(2,3); //which equ to val = m_data[x][y]

2. how to implement m_data[x][y] = val by Test class and what operator to overload?
if we overload just = operator then we will be able just
Test tst;
tst = 5; //but its not possible with this to provide x,y coeffs for m_data[x][y]

9ine

Re: Operator= overloading

toxcct29-Jun-05 6:30

toxcct

29-Jun-05 6:30

9ine wrote:
int Test::operator()(int x, int y)
{
//check if x,y out of range
return m_data[y][x];
}

it won't work until it returns an int (copy of the actual value... so, it is not an lvalue, an the compiler won't accept you to assign the result of the operator()().

use int& instead, as i did in my first answer[^]...

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Re: Operator= overloading

Member 341989129-Jun-05 19:33

Member 3419891

29-Jun-05 19:33

And how to be with class pointers?
with Test tst;
we get nice brief form:
int a = tst(3,2);
but with class pointer Test *tst1 = &tst;
we get bulky notation:
int b = tst1->operator()(3,2);
is it possible to something like tst(3,2) with pointer to class?

9ine

Re: Operator= overloading

toxcct29-Jun-05 20:11

toxcct

29-Jun-05 20:11

wohhhhh, no no no

use the defenrenciation operator...

Test *tst1 = &tst;
int b = (*tst1)(3, 2);

hope this helps you Wink | ;)

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Re: Operator= overloading

Member 341989129-Jun-05 23:12

Member 3419891

29-Jun-05 23:12

Thanks very much, I've done it completely and it works!

9ine

Re: Operator= overloading

toxcct30-Jun-05 0:11

toxcct

30-Jun-05 0:11

9ine wrote:
Thanks very much, I've done it completely and it works!

Big Grin | :-D

you're welcome... i'm always happy when i reach helping people usefully...

ps: if you liked my post, don't forget to vote for it ! Poke tongue | ;-P

ps 2 : i edited my previous answer[^] to consider using pointers.

cheers dear, Rose | [Rose]

TOXCCT >>> GEII power
[toxcct][VisualCalc]

MFC controls. CListBox

mpuerto28-Jun-05 18:28

mpuerto

28-Jun-05 18:28

Hi,

I'm using VC7 and MFC.

I create a ListBox control using the dialog editor and the toolbox and I attach it a control variable of the type CListbox.

On the other hand I create another list manually, declaring a CListBox variable and calling Create.

I use AddString to add new items, but the fonts are different. The manually created list has some kind of bold font.

I have tried everything. Changing the create styles, trying to use CreateEx, but I cannot get they to look the same. Cry | :((

I have the same problem with combo boxes.

I would appreciate any idea. Can anybody help me?

Re: MFC controls. CListBox

Christian Graus28-Jun-05 18:30

Christian Graus

28-Jun-05 18:30

I think that the code that is generated for you to create the control you dragged on includes code to set the font. I believe it has a Font property, or something like that.

Christian Graus - Microsoft MVP - C++

Re: MFC controls. CListBox

mpuerto28-Jun-05 18:51

mpuerto

28-Jun-05 18:51

Thank you very much for your fast response.

I decided to create those controls manually because I have a dialog window with edit controls, list boxes and combo boxes.

If I use the dialog editor and attach the control variable to them, some work properly when I add data, but others raise the error ERROR_INVALID_WINDOW_HANDLE.
Confused | :confused:

And I do not destroy the dialog window or the controls.

Thank you again for our fast response.

Re: MFC controls. CListBox

Christian Graus28-Jun-05 19:03

Christian Graus

28-Jun-05 19:03

mpuerto wrote:
If I use the dialog editor and attach the control variable to them

How do you mean ?

Another way to do this if you have multiple things on the form, is to put them all there, and just hide the ones you don't want to see at any point in time.

Christian Graus - Microsoft MVP - C++

Re: MFC controls. CListBox

mpuerto28-Jun-05 19:19

mpuerto

28-Jun-05 19:19

I meant that I place a list box in the dialog, with the dialog editor (not coding, with the visual interface), right from the toolbox. Then I attach a control variable to the listbox with the wizard.

When I try to add new strings to the listbox with AddString, it raises the error I told you before. But if I do everything coding: declare a variable of type CListBox, call Create and then AddString it works properly.

Can it has something to do with the fact that I declare the dialog class as DECLARE_DYNAMIC?

Thank you again for the help and sorry for the misunderstanding.

Re: MFC controls. CListBox

Christian Graus28-Jun-05 19:31

Christian Graus

28-Jun-05 19:31

Oh, I get you now. I'm sorry, I really don't know the answer to that question.

Christian Graus - Microsoft MVP - C++

Re: MFC controls. CListBox

Jose Lamas Rios29-Jun-05 2:54

Jose Lamas Rios

29-Jun-05 2:54

mpuerto wrote:
When I try to add new strings to the listbox with AddString, it raises the error I told you before.

Any chance you are calling AddString() before the execution of your dialog's OnInitDialog()?

--
jlr
http://jlamas.blogspot.com/[^]

Re: MFC controls. CListBox

mpuerto29-Jun-05 3:11

mpuerto

29-Jun-05 3:11

Sorry, I think that's not the case. Because I call AddString when I press a button in the dialog. If I call InitStorage the same error takes place.

Thank you for answering.

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