Using Swift 3 Stopping a scheduledTimer, Timer continue firing even if timer is nil

Question

We call startTimer function to start a timer. When we wanted to stop it we call stopTimerTest function but after we called stopTimer function the timerTestAction keeps firing. T

Answer 1

Most likely you've called startTimer twice without calling stopTimerTest. If you do that, you'll lose your pointer to the original timer and never be able to invalidate it.

The typical approach is to manage invalidation as a part of setting:

var timerTest : Timer? = nil {
    willSet {
        timerTest?.invalidate()
    }
}

Then stopping is just setting to nil:

func stopTimerTest() {
    timerTest = nil
}