CODEWITHSUNDEEP
c++pointerspointer-to-member
han jin
han jin

Reputation: 75

C++ pointer to member function getting an error : not a function or function pointer

Here is what I have:

A class PostfixCalculator, with public member methods:

class PostfixCalculator
{

public:
    PostfixCalculator();

    int  top();
    int  popTop();
    void pushNum(int);
    void add();
    void minus();
    void multiply();
    void divide();
    void negate();
    bool empty();
    void pushSymbol(string);

and when I try to call a member function by pointer to member function, I tried something like the following (I know the method does not make much sense, it is just a test):

void PostfixCalculator::pushSymbol(string str)
{
    func f = &PostfixCalculator::add;
    this.*(f)();
}

However, I get the following compiler error:

> postfixCalculator.cpp:84:12: error: called object type 'func' (aka
> 'void (PostfixCalculator::*)()') is not a function or function pointer
>                 this.*(f)();
>                       ~~~^ 1 error generated.

I am using clang++ to compile my program, under fedora linux.

Upvotes: 0

Views: 929

Answers (2)

AnT stands with Russia
AnT stands with Russia

Reputation: 320481

Firstly, this is a pointer, meaning you have to apply ->* to it, but not .*. If you want to use .*, you have to dereference this with * first.

Secondly, function call operator () has higher priority than .* or ->* operators, meaning that you need extra parentheses to make sure that the pointer f is dereferenced first, and the function call () is applied to the result of that dereference.

Should be

(this->*f)();

or alternatively

(*this.*f)();

Upvotes: 2

0xFFFFFFFF
0xFFFFFFFF

Reputation: 852

this is a pointer so you should use -> and deref * have lower priority than function call (), so you should use (this->*f)()

Upvotes: 0

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