Question

Here is a simplified version of what I have (not working):

prog.h:

...
const string c_strExample1 = "ex1";
const string c_strExample2 = "ex2";
const string c_astrExamples[] = {c_strExample1, c_strExample2};
...

prog.cpp:

...
int main()
{
    int nLength = c_astrExamples.length();
    for (int i = 0; i < nLength; i++)
        cout << c_astrExamples[i] << "\n";
    return 0;
}
...

When I try to build, I get the following error:
error C2228: left of ‘.length’ must have class/struct/union

The error occurs only when I try to use member functions of the c_astrExamples.
If I replace “c_astrExamples.length()” with the number 2, everything appears to work correctly.

I am able to use the member functions of c_strExample1 and c_strExample2, so I think the behavior arises out of some difference between my use of strings vs arrays of strings.

Is my initialization in prog.h wrong? Do I need something special in prog.cpp?

Answer 1

Arrays in C++ don’t have member functions. You should use a collection like vector<string> if you want an object, or compute the length like this:

int nLength = sizeof(c_astrExamples)/sizeof(c_astrExamples[0]);