Question

struct testing
{
    char lastname[20];        
};

testing *pt = new testing;            
pt->lastname = "McLove";

and I got

56 C:\Users\Daniel\Documents\Untitled2.cpp incompatible types in
assignment of ‘const char[7]’ to ‘char[20]’

Why ?

Thanks in advance.

Answer 1

Because compile time arrays are constant. In your struct testing, you have an array of 20 chars, and you’re trying to assign a pointer ("McLove", a compile time string, e.g., a const char*) to an array (a char[]), which won’t work.

To copy the data "McLove" into the array, you need to use strncpy:

strncpy(pt->lastname, "McLove", 20); // 20 is the size of the array, change it when your array size changes, or better yet, use a constant for both

Or better yet, use std::string:

struct testing {
    string lastname;
};

testing* pt = new testing;

pt->lastname = "McLove";

And now that will work, because std::string has an operator= that works with const char*.

As a side note, don’t needlessly allocate objects on the free store (using new); allocate them on the stack:

testing pt; // not: testing* pt = new testing;

testing.lastname = "McLove"; // with std::string