Why does this Coroutine only run once?

Question

"Something" is only printed once...

IEnumerator printSomething;

void Start () {

    printSomething = PrintSomething();
    StartCoroutine (printSomething);

}

IEnumerator PrintSomething () {

    print ("Something");

    yield return null;
    StartCoroutine (printSomething);

}

Answer 1

The misstake in your approach is that you save the enumerator. A enumerator is already "enumerating" therefore giving the enumerator to the StartCoroutine-method twice basically results in direct exit of the coroutine as the enumerator has been used before. Starting the coroutine again can be done by calling the function again.

StartCoroutine(PrintSomething());

But instead of starting the coroutine over and over again try to use a loop inside instead.

while (true)
{
    print("something");
    yield return null;
}

This is better as internal handling of the coroutine and its overhead is unknown.

Answer 2

Try co-routine's name instead of a pointer. Or co-routine itself.

IEnumerator PrintSomething () 
{
    print ("Something");

    yield return null;

    StartCoroutine ("PrintSomething");
}

Or

IEnumerator PrintSomething () 
{
    print ("Something");

    yield return null;

    StartCoroutine (this.PrintSomething());
}