Wsrtjtyk

I'm new to C++ programming and in my OPP class we were requested to create a phone book.

Now, in the lecture the Professor said something about that if you want to make sure that your variable that is being injected to a method doesn't get changed you must put const on it.

here is my code so far.

private:

 static int phoneCount;

 char* name;

 char* family;

 int phone;

 Phone* nextPhone;



public:

    int compare(const Phone&other) const;

    const char* getFamily();

    const char* getName();

and in Phone.cpp

int Phone::compare(const Phone & other) const

{

 int result = 0;

 result = strcmp(this->family, other.getFamily());

 if (result == 0) {

    result = strcmp(this->name, other.getName);

 }

 return 0;

}

I keep getting "the object has type qualifiers that are not compatible with the member"
when I try to call to strcmp inside my compare function.
I know that I can just remove the const in the function declaration and it will go away, but I still doesn't understand why it's showing in the first place.

Help would be greatly appreciated.

You need to add const qualifier for getters const char* getFamily() const;. This way these getters can be invoked on objects of type const Phone & that you pass into function.

Also other.getName should be other.getName().

In addition to the other answers that correctly suggest const qualifying your getters, you can access the data members of other directly, avoiding those calls.

int Phone::compare(const Phone & other) const

{

 int result = strcmp(family, other.family);

 if (result == 0) {

    result = strcmp(name, other.name);

 }

 return result;

}

Your signature

int Phone::compare(const Phone & other) const

means inside that function you need to ensure you don't change the Phone instance.

At the moment, your function calls const char* getFamily() (and getName, which you've missed the () call from). Neither of these functions are const, hence the error.

If you mark these as const too, it will be ok.