Copying Data Instead of Memory Addresses

[Jack]

I am currently trying to work on a program and I found it more convient to
have a tempory object which would hold a copy of data loaded from a file so I
wouldn't have to work with the overhead of loading from a file repeatedly.
My problem is that when I store the temporary object to another object,
changing the temporary object or its data also changes the data of the other
object.

Example:

MyClass a=new MyClass(2), b=new MyClass(3);
b=a;
a.data=10;
//b's data field now also equals 10 although what I really wanted to do was
//copy the integer data and keep it the same even if a's data field changed.

Since my objects are more complex than just one integer, I don't want to
have to manually move all the data and since there are also some objects
(such as Bitmaps) in the temporary object, so I would be unable to move the
data by hand without incurring the error described above.

Is there any way to create a copy of one object in such a way that the data
of the copy is not changed when the data of the original is changed?

Thank you.

[Chris]

Re: Copying Data Instead of Memory Addresses

This is how it should be. Look at what you are doing.

Here create a pointer to a class and call that pointer "a" and create and
object that "a" now points to.
MyClass a=new MyClass(2),

Here create a pointer to a class and call that pointer "b" and create and
object that "b" now points to.
b=new MyClass(3);

now have b point to the same object a and forget all about the object b
pointed to.
b=a;
a.data=10;

You have to make a copy of "a" in order to do what you want.

MyClass a, b
a = new MyClass(2)
b = a.makecopy()

hope this helps
Chris


"Jack" <Jack@discussio ns.microsoft.co m> wrote in message
news:A639CEA4-170F-4D9B-9575-5086AC5D3DF0@mi crosoft.com...[color=blue]
>I am currently trying to work on a program and I found it more convient to
> have a tempory object which would hold a copy of data loaded from a file
> so I
> wouldn't have to work with the overhead of loading from a file repeatedly.
> My problem is that when I store the temporary object to another object,
> changing the temporary object or its data also changes the data of the
> other
> object.
>
> Example:
>
> MyClass a=new MyClass(2), b=new MyClass(3);
> b=a;
> a.data=10;
> //b's data field now also equals 10 although what I really wanted to do
> was
> //copy the integer data and keep it the same even if a's data field
> changed.
>
> Since my objects are more complex than just one integer, I don't want to
> have to manually move all the data and since there are also some objects
> (such as Bitmaps) in the temporary object, so I would be unable to move
> the
> data by hand without incurring the error described above.
>
> Is there any way to create a copy of one object in such a way that the
> data
> of the copy is not changed when the data of the original is changed?
>
> Thank you.[/color]

[Bruce Wood]

Re: Copying Data Instead of Memory Addresses

You want your class to implement the ICloneable interface.

You can then copy the object by saying

MyClass b = a.Clone();

However, you do have to write Clone() yourself, and define what
"cloning" means for your class....

[Bruce Wood]

Re: Copying Data Instead of Memory Addresses

You want your class to implement the ICloneable interface.

You can then copy the object by saying

MyClass b = a.Clone();

However, you do have to write Clone() yourself, and define what
"cloning" means for your class....