Creating Images in Borland C++ 6

[stovellp]

Gidday

I'm using borland CBuilder 6 on windows 2000 and I want to create an array of Images, the same as the VCL TImage.

It lets me create an array of TImages, but It wont let me write

TImage * MyImages[10];

MyImages[0] = new TImage;

because TImage has no default constructor (which I found a bit strange, as I though all classes have constructors as default).

Any Ideas how I could get around this?

Paul

[Polymorphic OOP]

You could derive a class from TImage and give it a default constructor. Then you can make an array of instances of it rather than of TImage.

EDIT: Didn't notice you were dynamically allocating. You shouldn't have a problem -- see later reply...

[stovellp]

Thanks mate! I never thought of that. Thanks very much.

[stovellp]

Sorry, I just tried it. It wont compile because theres no Constructor for TImage. This is what I have:

// PImage is the name of my derived class
PImage * myImages[10];

myImages[0] = new PImage;

Error: Could not find constructor for base class TImage...

[Polymorphic OOP]

There has to be at least 1 constructor otherwise you wouldn't be able to make instances of the class at all.

How do you normally go about making an instance the TImage class?

[stovellp]

Normally I just click "Image" and drag it where I want it on the form, the IDE takes care of all the code stuff as far as creating objects goes.

When the IDE creates a TImage, it writes "TImage * Image1" or whatever you chose to call it, into te header file. Then (I think) it creates data files that hold info about the object. Trouble is, I can create instances of other object like TBitmap (Part of a TImage) just fine.

[stovellp]

I just did a search through every file in the Include directory for "class TImage" and it couldn't find it.

[Polymorphic OOP]

You're dynamically allocating, why don't you just call the constructor explicitly when you allocate each one? You shouldn't be having any problems. You shouldn't need to create a child class or anything (I only suggested this because I though you were making an array of objects, not pointers).

[Polymorphic OOP]

You should be able to find information about the constructor somewhere. It has to be in the headers somewhere, you must've missed it. If you can't find it, I'm sure there's plenty of documentaiton you should be able to find. Are you sure it has a public constructor? Perhaps you're not supposed to have direct access to any of it's constructors.

Don't search for "class TImage" because it might be a struct, union, or a typdef of one of them, etc.

[stovellp]

Okay, so Instead on myImages[0] = new PImage, I have now got myImages[0]->PImage();

Now It is telling me there is no such thing as PImage, and if even if i specify it, I get the same message I was getting earlier plus PImage() doesn't exist, WHEN I JUST DECLARED IT! lol.

[Polymorphic OOP]

Originally posted by stovellp
Okay, so Instead on myImages[0] = new PImage, I have now got myImages[0]->PImage();

Now It is telling me there is no such thing as PImage, and if even if i specify it, I get the same message I was getting earlier plus PImage() doesn't exist, WHEN I JUST DECLARED IT! lol.

No, not like that. You can't call a constructor like that -- besides you still have to dynamcially allocate memory for it.

You have to do something like:

myImages[0] = new PImage( parameters go here );

But I have a strong suspicion that you're working with TImage completely wrong. The constructors are probably not public functions. Look for documentation on that class and find out what its constructors are, or just use that "drag and drop" and then look at the corresponding code it creates.

[stovellp]

Yeah, looks like I'll have too. I was hoping not to have to use the documentation because its soooo long. Thanks anyway mate, see ya next month when I've finished looking (and haven't solved it).

[Davros]

To create a TImage at runtime, do the following:

TImage *img = new TImage(NULL);

It's only contructor accepts TComponent pointer to hold as reference of the object responsible for destroying the TImage. You can pass it NULL(0) if you like. I wouldn't bother deriving a class from TImage for what you want to do.

Because you have created a TImage instance yourself at runtime, don't forget to destroy it - it won't be destroyed automatically like components dragged onto the form in the IDE.

If you want your TImage object to be shown, you need to attach it to a parent window, like so:

img->Parent = Form1;

That's all there is to it. However, if you just want to hold an array of bitmaps, you could use TBitmap instead of TImage. A bitmap can be copied into an TImage component at anytime using:

Image1->Picture->Assign( bmp );