class A{
private : string a[3];
public : A();
void ShowA();
}
A::A(){ string a[3] = {"aa","bb","cc"} }
void A::ShowA(){
for(int x=0;x<=2;x++){
cout<< a[x];
}
}
int main(){
A a;
a.ShowA();
return 0;
}
In this code, I think the output is aabbcc but there is nothing. Just blank is existed. Could you tell me why it happens and how to fix it. Cheers guys.
As the comments tell you, you are creating a local variable a inside your constructor, instead of setting the value of the attribute a. You can set the value of a in member initializer list.
The code becomes
#include <iostream>
#include <string>
using namespace std;
class A {
private:
string a[3];
public:
A();
void ShowA();
};
A::A() : a{"aa"s, "bb"s, "cc"s} {}
void A::ShowA() {
for(int x = 0; x <= 2; x++) {
cout << a[x] << std::endl;
}
}
int main() {
A a;
a.ShowA();
return 0;
}
Note: The 's' after the "aa", "bb" and "cc" strings is a string literal. It is not really necessary in this case, since the compiler know you are creating an array of std::string objects.
A::A() : a{"aa"s, "bb"s, "cc"s} {} what is s mean??
You are re-defining the string "a" in the constructor, you should simply assign it in the constructor instead of using the "string" type again. If you give the type again it creates a local variable available in the scope of the constructor only.
string a[3]in your constructor creates a new local variable (completely unrelated to member variable with the same name), which is immidiately discarded. See Initializing a member array in constructor initializer or C++ Initializing Non-Static Member Array for a more modern approach.aand assigning to a local variable that's later discarded.aand in the constructor you have anathat is local to the constructor. Read about scope (andstd::arrayand initialization of members)std::vectorhere.