Object Initialization in C++

[Venkat]

Hello All.

I am having a trouble creating a Object in Case Label, and calling the
Member Function outside the Switch. Can some one please help me..??

My code looks like

int main()
{
int number;
cout <<"1. Chevy"<<endl;
cout << "2. Toyota"<<endl;
cout << "enter a number"<<endl;
cin >> number;
switch(number)
{
case 1:
{
Chevy o;
}
break;
case 2:
{
Toyota o;
}
break;
default:
{
Auto o;
}
break;
}
o.Description() ;
return 0;
}


In this case I want to call the Description Member Function depending
on the Object.

But the Compiler does not know about "o". How can I implement this.??


Thanks in advance
-Venkat

[tom_usenet]

Re: Object Initialization in C++

On 3 Oct 2003 07:44:30 -0700, junnuthula@yaho o.com (Venkat) wrote:
[color=blue]
>Hello All.
>
>I am having a trouble creating a Object in Case Label, and calling the
>Member Function outside the Switch. Can some one please help me..??[/color]

Once an automatic object has gone out of scope, it no longer exists,
so you can't possibly call member functions of it.
[color=blue]
>
>My code looks like[/color]

What about Chevy, etc.? Do they all derive from Auto?
[color=blue]
>
>int main()
>{
> int number;
> cout <<"1. Chevy"<<endl;
> cout << "2. Toyota"<<endl;
> cout << "enter a number"<<endl;
> cin >> number;
> switch(number)
> {
> case 1:
> {
> Chevy o;
> }
> break;
> case 2:
> {
> Toyota o;
> }
> break;
> default:
> {
> Auto o;
> }
> break;
> }
> o.Description() ;
> return 0;[/color]

Instead:

int number;
cout <<"1. Chevy"<<endl;
cout << "2. Toyota"<<endl;
cout << "enter a number"<<endl;
cin >> number;
Auto* o = 0;
switch(number)
{
case 1:
{
o = new Chevy;
}
break;
case 2:
{
o = new Toyota;
}
break;
default:
{
o = new Auto;
}
break;
}
o->Description( );
delete o;
return 0;
}
[color=blue]
>In this case I want to call the Description Member Function depending
>on the Object.
>
>But the Compiler does not know about "o". How can I implement this.??[/color]

Using polymorphism. Auto should look like this:

class Auto
{
public:
virtual ~Auto();
virtual void Description();
};

And the others should override Description.

Tom

[Josephine Schafer]

Re: Object Initialization in C++


"Venkat" <junnuthula@yah oo.com> wrote in message
news:86545ff.03 10030644.479114 2c@posting.goog le.com...[color=blue]
> Hello All.
>
> I am having a trouble creating a Object in Case Label, and calling the
> Member Function outside the Switch. Can some one please help me..??
>
> My code looks like
>
> int main()
> {
> int number;
> cout <<"1. Chevy"<<endl;
> cout << "2. Toyota"<<endl;
> cout << "enter a number"<<endl;
> cin >> number;
> switch(number)
> {
> case 1:
> {
> Chevy o;
> }
> break;
> case 2:
> {
> Toyota o;
> }
> break;
> default:
> {
> Auto o;
> }
> break;
> }
> o.Description() ;
> return 0;
> }
>
>
> In this case I want to call the Description Member Function depending
> on the Object.
>
> But the Compiler does not know about "o". How can I implement this.??
>[/color]
A simple way would be to declare a base class Vehicle.
Derive Chevy, Toyota and Auto from it.
Declare Description to be a virtual function in Vehicle.
Then declare Vehicle *p = NULL;
.....
{
case 1:
p = new Chevy;
case 2:
//
case 3:
// so on ..
}
// then call description
p ->Description ();
delete p;

Don't forget to declare the destructor in Vehicle class to be virtual.

HTH,
J.Schafer

[David Rubin]

Re: Object Initialization in C++

Venkat wrote:[color=blue]
>
> Hello All.
>
> I am having a trouble creating a Object in Case Label, and calling the
> Member Function outside the Switch. Can some one please help me..??[/color]

[snip][color=blue]
> switch(number)
> {
> case 1:
> {
> Chevy o;
> }[/color]

What is the scope of o in the above example?

In any case, a more correct solution has been given.

/david

--
Andre, a simple peasant, had only one thing on his mind as he crept
along the East wall: 'Andre, creep... Andre, creep... Andre, creep.'
-- unknown

[red floyd]

Re: Object Initialization in C++

Josephine Schafer wrote:[color=blue]
> "Venkat" <junnuthula@yah oo.com> wrote in message
> news:86545ff.03 10030644.479114 2c@posting.goog le.com...
>[color=green]
>>Hello All.[/color][/color]
[switch statement from hell redacted][color=blue][color=green]
>>[/color][/color]
[simple and lucid explanation and solution redacted][color=blue]
>
> Don't forget to declare the destructor in Vehicle class to be virtual.
>[/color]
He should also look into the Factory pattern.