accessing struct variable inside getter setter in a c++ class

Question

Okay, I have something like this in C++:

class MyClass{
private:
  int someVariable;
  int someOtherVariable;

  struct structName{
    int someStructVariable;
    int someOtherStructVariable;
  };//end of struct

public:
  //getters & setters for the defined variables.

  int getSomeStructVariable()
  {
    // this does not work I get this error: "error: expected primary-expression
    // before '.' token"
    return structName.someStructVariable;
  } 
};//end of class

How should I write my getter or setter in this case?

Answer 1

structName is part of the type name, not the variable name. You need to give it a name, something like:

struct structName {
  int someStructVariable;
  int someOtherStructVariable;
} myStructure;

And then in your accessor use:

return myStructure.someStructVariable;

That should get you the result you want. Other alternatives for the structure variable are to separate out the structure definition from the variable declaration:

struct structName {
  int someStructVariable;
  int someOtherStructVariable;
};

struct structName myStructure;

or to add in typedef:

typedef struct structName {
  int someStructVariable;
  int someOtherStructVariable;
} structTypedefName;

structTypedefName myStructure;

Answer 2

struct A {
  A() : _n(0) {}
  int get_n() const {
    return _n;
  }
  void calculate(int a) {
    _n = a * a * a;
  }
private:
  int _n;
};

Here's a complete example. If you want a mirror set_n instead of something which manipulates the data, then you should probably drop the getter/setter (as you'd be using them incorrectly) and make the data member public.

Also, remember: defining classes with struct works identically to defining classes with class but for one exception: public instead of private as the default access for members and bases.

Answer 3

It is not a good idea to write a getter/setter for each structure field. A better solution is:

typedef struct {
    int field1;
    int field2;
} structType;

class MyClass {
private:
    structType _structName;
public:
    const structType & getStructName() const {
        return _structName;
    }
}

Keep structType and MyClass separate. Use the getter as:

MyClass m;
int var;
var = m.getStructName().field1;

The first const is needed to return a const value. The second one is needed for const-correctness.

There are two ways to define a setter:

class MyClass {
// ...
public:
    // type 1
    void setStructName(const structType &s) {
        _structName = s;
    }
    // type 2
    structType & setStructName() {
        return _structName;
    }
}

Use the first one as:

MyClass m;
structType s;
m.setStructName(s);

The second version enables you to modify separate structure fields as well:

m.setStructName() = s;
m.setStructName().field1 = 10;

Note that the setter might need some adjustments if the structure contains pointers.