declaring a pointer or a stack variable

Question

Assume we have the following case:

• If it is morning mood is good otherwise mood is bad
• Print the mood

it could be written as:

std::string mode; //this cost us calling the constructor of std::string
if(time==Morning){ // a real code should be here
   mood="Good"//re assign the string
}
else{
   mood="bad"//re assign the string
}
std::cout << mood;

assuming it is not std::string, it is a very big object. Isn't it too luxury to declare "mode" and call the constructor for no reason! Is using the raw pointer a solution? what is the best practice here? thanks

Answer 1

You could use the ternary operator to initialize the string.

std::string mode = (time == Morning ? "Good" : "Bad")

As MSalters pointed out in the comments this is actually still two constructions(constructor + copy) but it should get optimized by the compiler. You can directly initialize the string with

std::string mode { (time == Morning ? "Good" : "Bad") };

Answer 2

I would consider putting the logic into a separate function. This helps to keep functions small and simple.

std::string moodAtTime(Time time)
{
    if(time==Morning)
    { // a real code should be here
        return "Good";
    }
    else
    {
        return "bad";
    }
}

std::string mood = moodAtTime(t);

This reduces function length and splits the code into small units performing simple questions.

If it is only for initialization, you can use a lambda to do it without the named function:

std::string mood = [](Time t)
{
    if(t==Morning)
    { 
        return "Good";
    }
    else
    {
        return "bad";
    }
}(now);