setLifespan method
A control method allowing a parent of this Particle
to pass down it's
lifespan.
Allows to only specify desired lifespan once, at the very top of the
Particle
tree which then will be propagated down using this method.
See SingleChildParticle
or ComposedParticle
for details.
Implementation
void setLifespan(double lifespan) {
// TODO(wolfenrain): Maybe make it into a setter/getter?
_lifespan = lifespan;
_timer?.stop();
_timer = Timer(lifespan, onTick: () => _shouldBeRemoved = true)..start();
}