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Prevent Implicit Typecast (C++)

Started by Kustaz Sep 1, 2006 at 4:07 AM 4 replies 1.3k views

Original Post

Sep 1, 2006 at 4:07 AM

Ok, lets say I have 2 classes; A and B. A is at heart, B, but more specialised. I Can convert an A to a B, And can multiply an A by a B. However, I cant multiply an A by an A. But, since an A can be converted to a B, a typecast is implicitly applied, and an incorrect result is achieved! how can I prevent this implicit typecast from occuring? Thanks in advance.

Nitage

125

Nitage

Sep 1, 2006 at 4:27 AM

By what mechanism is A being converted to B?

Kustaz

Author

Kustaz

Sep 1, 2006 at 4:38 AM

A typecast operator, for example:

operator B(A arg_)
{
return arg_.Data;
}

Nitage

125

Nitage

Sep 1, 2006 at 4:45 AM

Remove that operator and replace it with an explicit constructor in B:

class B{...public:    explicit B(A arg_)        :data_(arg.Data)    {    }...};

The c'tor allows conversion from A to B, but because it's marked explicit it won't implicitly convert.

Kustaz

Author

Kustaz

Sep 1, 2006 at 5:01 AM

Thanks Nitage, you've been very helpful, i now have my code working.

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