C++ code error in my practice code [closed] - c++

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Can you please help me out with this issue?
#include <iostream>
#include <cstring>
using namespace std;
class A
{
public:
char str[4];
A()
{
str = "C++";
cout << "Constructor A" << endl;
}
void display()
{
cout << str << " is your name" << endl;
}
};
int main()
{
A a;
a.display();
return 0;
}
It gives the following errors:
**************************Error**********
StringProg.cpp:9: error: ISO C++ forbids initialization of member "str"
StringProg.cpp:9: error: making "str" static StringProg.cpp:9: error: invalid in-class initialization of static data member of non-integral type "char [4]"
StringProg.cpp: In member function "void A::display()":
StringProg.cpp:17: error: "str" was not declared in this scope
**************************

Answer 1

There are quite a few issues with C arrays that prevent you from doing what you want to do.
String literals have type of const char[n] (n being their length + 1 for \0 character). To use them in C Standard Library functions, they decay to const char*, which don't carry the size of the string, and in order to find it, the strings need to be traversed (every character being looked at and compared to \0)
As a consequence, array assignment operator would need to be rather nontrivial; this isn't provided by the language, and you have to use library functions like strcpy to move the literal into your usable memory. In other words, you can't assign C arrays like other values.
Arrays function in a very primitive way; they don't have operators for comparison, it's harder to pass them to functions and store in the classes properly.
And so, because of all the above...
Prefer std::string to char[]:
class A {
std::string str;
public:
// prefer constructor init list
A() : str("C++") {
// your line would work, too
std::cout << "Constructor A" << std::endl;
}
void display() const {
std::cout << str << " is your name" << std::endl;
}
};
int main()
{
A a;
a.display();
// return 0; is unnecessary
}
Some "rules of thumb" (rules of thumbs?): if you need more than one element, start with vector<>. Never use C arrays. string is one element, not an "array of characters".

Answer 2

Try the following
#include<iostream>
#include<cstring>
class A
{
private:
char str[4];
public:
A() : str { "C++" }
{
std::cout << "Constructor A" << std::endl;
}
void display() const
{
std::cout << str << " is your name" << std::endl;
}
};
int main()
{
A a;
a.display();
return 0;
}
The program output is
Constructor A
C++ is your name
Take into account that arrays do not have the copy assignment operator. Thus this statement in your program
str = "C++';
even if to update the typo and write
str = "C++";
is invalid.
You could use standard C function strcpy declared in header <cstring>. For example
#include <cstring>
//...
A()
{
std::strcpy( str, "C++" );
std::cout << "Constructor A" << std::endl;
}