C ++中具有类/对象的逻辑运算符

Question

Completely new to C++. Trying to understand classes and objects, so far I get the gist of it, as it's nothing too complicated for the very basics. However, this code I have wrote is not working as intended. It works somewhat, however it asks for user input twice.

#include <iostream>
#include <string>
using namespace std;

class FooFoo {
public :

string GetName() {
    cin >> name;
    return name;
}

private:
    string name;
};

int main()
{
FooFoo object;
if (object.GetName() == "John" || object.GetName() == "Chris")
{
    cout << "Yes";

}
else {
    cout << "No";
}

}

If I input "John", it will return yes right away. However, when I input anything else, it will prompt me to enter something again, and then the if/else acts accordingly to whatever I inputted.

Answer 1

You call object.GetName() twice which causes the input to be asked for twice. Store the result of this function to a variable and use that in the if statement. The || statement is short-circuited if the first expression is true. This leads to the second call not being executed if the first is true.

Answer 2

That is because GetName() is asking for input every time,

So the first time it is asking for x, if x isnt john it goes to the next test, which then gets input and tests that against x = chris.

try changing it to this:

int main()
{
FooFoo object;
string test = object.GetName()
if (test == "John" || test == "Chris")
{
    cout << "Yes";

}
else {
    cout << "No";
}

}

Hope that helps

Answer 3

Your current if statement effectively evaluates to:

if (object.GetName() == "John")
  cout << "Yes";
else if (object.GetName() == "Chris")
  cout << "Yes";
else
  cout << "No";

Try entering Chris followed by John and you should get No .

Just call getName() before the if statement, store the value in a local variable, then test that instead:

string name = object.GetName();
if (name == "John" || name == "Chris")
  cout << "Yes";
else
  cout << "No;