class A
{
public:
A(B);
~A();
};
class B
{
public:
B(A);
~B();
};
2 classes that are dependant on each other
Author
how can i have something like this
You can have a forward declaration.
But in your case, how could you ever create either A or B, when the constructors of both need an object of the other type?
But in your case, how could you ever create either A or B, when the constructors of both need an object of the other type?
As is, that is impossible. In order to create an instance of A, one needs a B instance, and to make a B an A needs to exist.
Without the actual context (which is typically important, most such problems can be designed around) it is hard to give any concrete advice. For example, instead of B having an A as a member, it might be possible to pass an A instance to member functions of B that require an A. Or, it might be possible to use a reseatable reference, like a (smart) pointer, on one side of the relationship.
Without the actual context (which is typically important, most such problems can be designed around) it is hard to give any concrete advice. For example, instead of B having an A as a member, it might be possible to pass an A instance to member functions of B that require an A. Or, it might be possible to use a reseatable reference, like a (smart) pointer, on one side of the relationship.
Author
what if only one of the classes above needed to be passed in the other class through the constructor.
like this
i think i still have the same problem
like this
class A{public: A(); ~A(); SomeFunc() { //create instance of class B and do stuff }};class B{public: B(A); ~B();};i think i still have the same problem
Quote:Original post by b1gjo3
i think i still have the same problem
No, A can use the this pointer to create B:
void A::SomeFunc() { B(*this); //...}
just one extra point - unless you want B to have a copy of A then
B(const A&) or B(A&) would make more sense. And then you could call
B(const A&) or B(A&) would make more sense. And then you could call
void A::SomeFunc(){ B(this); //...}
Author
Quote:Original post by Gage64Quote:Original post by b1gjo3
i think i still have the same problem
No, A can use the this pointer to create B:
*** Source Snippet Removed ***
when i do this, i get an error saying the class has no constructors
Post the actual errors.
If you have changed the code quite a bit, post the updated code.
This works for me:
If you have changed the code quite a bit, post the updated code.
This works for me:
class A{public: A(int value) : value(value) {} void SomeFunc(); int value;};class B{public: B(const A &a) : a(a) {} void foo() { std::cout << a.value << std::endl; }private: A a;};void A::SomeFunc(){ B b(*this); b.foo();}int main(){ A a(42); a.SomeFunc();}
Your code snippet only contains constructor/destructor declarations. Did you give them a definition as well?
Here's an example definition for A's constructor:
If that's not it, post the exact error you are getting.
Here's an example definition for A's constructor:
A::A(){ cout << "I'm A's constructor!" < endl;}If that's not it, post the exact error you are getting.
Without knowing what you intend on doing with A and B the easy solution is to create a thrid class C. And make C the base class that A and B derive from.
And make sure that whatever fields you need from A in B.. and from B in A.. exist within C. Thus you can generate a Class C, and use that to generate A and B as necessary. Also, A and B both do not require eachother to build or compile, and they'll have a common naming scheme for all shared data (represented by class C).
Hope that helps.
Class C{ C();};Class A : public C{ A(C &c);};Class B : public C{ B(C &c);};And make sure that whatever fields you need from A in B.. and from B in A.. exist within C. Thus you can generate a Class C, and use that to generate A and B as necessary. Also, A and B both do not require eachother to build or compile, and they'll have a common naming scheme for all shared data (represented by class C).
Hope that helps.
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