Object scope and lifetime in a for loop

Question

Suppose I have the following code.

vector<Cat> v; \\Cat is a class
for (int i = 0; i < 5; i++)
{
    Cat cat1;
    if (someFunction(i))
    {
        cat1.setName("Whiskers");
        v.push_back(whiskers) ;
    }
}

My question is, in a for loop, does the object cat1 go out of scope while executing 0 to 4? That is will the destructor get called 5 times here or just once?

I guess you could have found an answer elsewhere without asking, though — Paolo M, Nov 20 '15 at 11:30
Why not just put some `cout` in the constructors/destructors? An instance answer — Ed Heal, Nov 20 '15 at 11:42

AndreyS Scherbakov · Accepted Answer · 2015-11-20T11:46:39.223

2

Constructor and destructor are called 5 times, right.

Because control flow crosses 5 times the initialization of cat, and 5 times the end of its scope (the closing '}' of loop block).

Actually, what you see in the outermost brace is actually one composite statement repeated while the loop condition (i < 5) is true.

edited Nov 20 '15 at 11:46

answered Nov 20 '15 at 11:29

AndreyS Scherbakov

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So in essence, a for loop is actually exiting at each i, then reentering the brackets? – Kevin Zakka Nov 20 '15 at 11:30
What about copy / move constructor in push_back()? It is called 5 times as well – Sukces Elektroniki Nov 20 '15 at 11:33
copy constructor in push_back of course called as frequently as push_back itself, 5 times – AndreyS Scherbakov Nov 20 '15 at 11:35

Object scope and lifetime in a for loop

1 Answers1