Question

It can be simple but I m new about c++
In char arrays we can let the compiler to count number of characters in the string like

char myarray[]="stringvar";

its ok, but if i change the code as below,the compiler gives error

string myvar = "stringvar";
char myarray[] =myvar;

error: initializer fails to determine size of myarray

Why is that?

Answer 1

You can do this:

string myvar = "stringvar";
const char * myarray = myvar.c_str(); //immutable string

In this case, the data whichmyarray points to, lives as long as the lifetime of myvar.

However, if you want a mutable string or, a string which may last longer (or shorter) than the lifetime of myvar, then you’ve to allocate memory yourself as:

char * myarray = new char[myvar.size()+1]; //mutable string
std::strcpy(myarray, myvar.c_str());

//you've to deallocate the memory yourself as:
delete [] myarray;