classes in unions?

[uralmutlu]

Hi,

I was wandering if I can have classes in unions?

I basically have source code in a format very similar to:

union example {
ClassA variable1;
ClassB variable2;
};

class AnotherClass {
.....
example SomeName;
.....

};

However, the compiler (gcc) tells me constructors aren't allowed in
unions.

I have a very large program written for eg ClassA, and I am adding a
second class, eg ClassB, to it. I came to this particular code, and I
thought unions would be an easy solution, but it looks like I will have
to make other changes.

I thought since classes are types they would be allowed in unions.

so no classes in unions?

regrads

 

[Ian Collins]

Hi,

I was wandering if I can have classes in unions?

I basically have source code in a format very similar to:

union example {
ClassA variable1;
ClassB variable2;
};

class AnotherClass {
.....
example SomeName;
.....

};

However, the compiler (gcc) tells me constructors aren't allowed in
unions.

I have a very large program written for eg ClassA, and I am adding a
second class, eg ClassB, to it. I came to this particular code, and I
thought unions would be an easy solution, but it looks like I will have
to make other changes.

I thought since classes are types they would be allowed in unions.

so no classes in unions?

Think about it - which constructor initialises the object?

Unions are rare in C++ (compared to C), C++ offers more appropriate
solutions. Unions are often used as a poor man's polymorphism in C.

 

[Frederick Gotham]

(e-mail address removed) posted:

I was wandering if I can have classes in unions?

Yes, but each member of the union must be a POD.

 

[loufoque]

I was wandering if I can have classes in unions?

See boost.variant.

 

[Jim Langston]

Hi,

I was wandering if I can have classes in unions?

I basically have source code in a format very similar to:

union example {
ClassA variable1;
ClassB variable2;
};

class AnotherClass {
....
example SomeName;
....

};

However, the compiler (gcc) tells me constructors aren't allowed in
unions.

I have a very large program written for eg ClassA, and I am adding a
second class, eg ClassB, to it. I came to this particular code, and I
thought unions would be an easy solution, but it looks like I will have
to make other changes.

I thought since classes are types they would be allowed in unions.

so no classes in unions?

regrads

Instead of a union, I think polymorphism would work better for you.