•
•
•
•
What is DaniWeb IT Discussion Community?
You're currently browsing the C++ section within the Software Development category of DaniWeb, a massive community of 361,894 software developers, web developers, Internet marketers, and tech gurus who are all enthusiastic about making contacts, networking, and learning from each other. In fact, there are 2,239 IT professionals currently interacting right now! Registration is free, only takes a minute and lets you enjoy all of the interactive features of the site.
Please support our C++ advertiser:
Views: 5051 | Replies: 6
 |
•
•
Join Date: May 2005
Posts: 21
Reputation: 
Rep Power: 4
Solved Threads: 0
Newbie Poster
Help : Pointers to array of class objects . Hi All
I am relatively new to the C++ world . Facing some problem , while initializing an array of objects .
Suppose i have a class Rectangle . I want to have a pointer to an array of objects to the class . How do i invoke the Class Constructor , for a paricular object in the arraylist.
<< moderator edit: added [code][/code] tags >>
Pplz Help
Best Regards
Varun
I am relatively new to the C++ world . Facing some problem , while initializing an array of objects .
Suppose i have a class Rectangle . I want to have a pointer to an array of objects to the class . How do i invoke the Class Constructor , for a paricular object in the arraylist.
class Rectangle
{
public :
int side1 , side2;
Rectangle(int,int);
Rectangle();
void get_area();
private :
protected :
};
Rectangle::Rectangle(int x, int y)
{
side1=x;
side2=y;
}
void Rectangle::get_area()
{
cout<<"Area :"<< side1*side2<<endl;
}
Rectangle *ptr_arr;
ptr_arr=new Rectangle[2] ; // pointer to an array of objects to the class
// Now how do i initialize the dimensions for the ptr_arr[1] object , using the constructors ???Pplz Help
Best Regards
Varun
•
•
Join Date: May 2005
Location: Kolkata
Posts: 32
Reputation:
Rep Power: 4
Solved Threads: 3
Light Poster
Hi Varun,
Just try this:
Just try this:
Rectangle *ptr_arr[2]; ptr_arr[0] = new Rectangle(10,20); ptr_arr[1] = new Rectangle(15,5);
•
•
Join Date: May 2005
Posts: 21
Reputation:
Rep Power: 4
Solved Threads: 0
Newbie Poster
Thnx a lot Sir !!!
That definately worked ......But just wanna know thw diff b/n
Approach 1
---------------
Rectangle * ptr_arr;
ptr_arr=new Rectangle[2];
Approach 2
---------------
Rectangle * ptr_arr[2];
ptr_arr[0]=new Rectangle;
ptr_arr[1]=new Rectangle;
Are the two approaches same ???
That definately worked ......But just wanna know thw diff b/n
Approach 1
---------------
Rectangle * ptr_arr;
ptr_arr=new Rectangle[2];
Approach 2
---------------
Rectangle * ptr_arr[2];
ptr_arr[0]=new Rectangle;
ptr_arr[1]=new Rectangle;
Are the two approaches same ???
•
•
Join Date: May 2005
Location: Kolkata
Posts: 32
Reputation:
Rep Power: 4
Solved Threads: 3
Light Poster
Rectangle * ptr_arr; ptr_arr=new Rectangle[2];
Rectangle::Rectangle();
But if u want to call the constructor:
Rectangle::Rectangle(int x, int y)
u should use
ptr_arr[0] = new Rectangle(10,20); ptr_arr[1] = new Rectangle(15,5);
•
•
Join Date: May 2005
Posts: 21
Reputation:
Rep Power: 4
Solved Threads: 0
Newbie Poster
Actually what i meant was , that is there any diff b//n the memory allocation / meathod scheme of the two ..leave alone the first query of constructors
The first approach shows an array of objects being pointed to ..by the ptr_arr pointer .
Does the second one , signify a pointer array or an object array initialization ....
Wat's the difference . (just suppose that , no constructor is involved0
I hope i am clear .....
Best Regards
Varun
The first approach shows an array of objects being pointed to ..by the ptr_arr pointer .
Does the second one , signify a pointer array or an object array initialization ....
Wat's the difference . (just suppose that , no constructor is involved0
I hope i am clear .....
Best Regards
Varun
•
•
Join Date: May 2005
Location: Kolkata
Posts: 32
Reputation:
Rep Power: 4
Solved Threads: 3
Light Poster
Look Varun, the main difference between these 2 is that the 1st one allocates the memory at the time of running (dynamic memory allocation). But the 2nd one does the same at both compile and run time. First it creates memory at the time of compilation (ie, static memory allocation) for the line :
Rectangle * ptr_arr[2];
and after that it again creates the memory at run time for :
ptr_arr[0]=new Rectangle;
ptr_arr[1]=new Rectangle;
So I think if there is no specific reason, the 2nd approach should be avoided.
Amit
Rectangle * ptr_arr[2];
and after that it again creates the memory at run time for :
ptr_arr[0]=new Rectangle;
ptr_arr[1]=new Rectangle;
So I think if there is no specific reason, the 2nd approach should be avoided.
Amit
|
•
•
•
•
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
•
•
•
•
•
•
•
•
DaniWeb C++ Marketplace
Linear Mode
- Array of Class Objects? (C++)
- Passing Class Objects, Instances (C++)
- Initializing an array as a class mamber (C++)
Other Threads in the C++ Forum
- Previous Thread: WriteLine Specifyng what line to write in a textfile
- Next Thread: Printing a Queue to file
