CODEWITHSUNDEEP
c++classstruct
Ediolot
Ediolot

Reputation: 531

Class pointer inside struct C++

The question is simple, I guess I cannot do this: (Im in the header file)

typedef struct {
     myclass *p;
     ...
 } mystruct;

class myclass {
     private:
          mystruct *s;
          ...
}

Because when the compiler reaches the struct it doesnt know what myclass is, but I cannot do the reverse either for the same reason:

class myclass {
     private:
          mystruct *s;
          ...
}

typedef struct {
     myclass *p;
     ...
 } mystruct;

How can I make that possible ? Im guessing there is some way to say the compiler "There is an struct called mystruct" before the class (2 example) so it knows that mystruct *s it's possible but I cant manage to do it right. Thanks

Upvotes: 1

Views: 3476

Answers (3)

flogram_dev
flogram_dev

Reputation: 42868

You need to use a forward declaration:

class myclass;

typedef struct {
     myclass *p;
     ...
 } mystruct;

class myclass {
     private:
          mystruct *s;
          ...
}

Now the compiler knows that myclass is a class when it first sees it.

Also, no need to typedef structs in C++. You can simply write:

struct mystruct {
     myclass *p;
     ...
};

Which does the same.

Upvotes: 10

FToDance
FToDance

Reputation: 315

First of all, typedefs shouldn't be used anymore in modern C++ (there is better syntax). For structs just use:

struct mystruct {
...
}

Also maybe consider a redesign so that you don't have 2 types dependent on each other. If it's not possible, then as others have said forward declare the types before.

Upvotes: 0

A.S.H
A.S.H

Reputation: 29352

In general, it is possible to declare a pointer to a class that has not been defined yet. You need only to have "declared" the class (class myclass).

This is the general solution to define classes with cross-references.

Upvotes: 1

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