以不同的持续时间重复倒数

Question

I would like to make a countdown ticker with 2 different durations. What is the best way to do this? I try to do this:

s5 := time.Tick(5 * time.Second)
m5 := time.Tick(5 * time.Minute)

for {
    select {
        case t := <-s5:
            ...
        case t := <-m5:
            ...
    }
}

But I need ticker for different intervals:

5:00 -> 0:00
0:05 -> 0:00
5:00 -> 0:00
0:05 -> 0:00

Which is idiomatic way to do this?

Answer 1

You could just call sleep if you want

dur := 1 * time.Second
nextDur := 3 * time.Second

for {
    time.Sleep(dur)
    dur, nextDur = nextDur, dur

    ...
}

Or alternate the durations in a time.Timer if you need to select. This is what I would personally stick with, since you don't need to worry about the offset between two timers skewing due to scheduling inconsistencies.

dur := 1 * time.Second
nextDur := 3 * time.Second

timer := time.NewTimer(dur)

for {
    select {
    case t := <-timer.C:
        dur, nextDur = nextDur, dur
        timer.Reset(dur)
        ...
    }
    ...
}

Or run 2 timers offset by the smaller interval

dur1 := 1 * time.Second
dur2 := 3 * time.Second

timer1 := time.NewTimer(dur1)
timer2 := time.NewTimer(dur1 + dur2)

for {
    select {
    case t := <-timer1.C:
        timer1.Reset(dur1 + dur2)
        fmt.Println("timer1:", t)
    case t := <-timer2.C:
        timer2.Reset(dur1 + dur2)
        fmt.Println("timer2:", t)
    }

}

And you could also run interleaved Tickers like you originally tried, but that requires a little more coordination to delay the start of one of them

dur1 := 1 * time.Second
dur2 := 3 * time.Second

ticker1 := time.NewTicker(dur1)
ticker2 := time.NewTicker(dur1 + dur2)

var once sync.Once
delayOnce := func() {
    ticker1.Stop()
    ticker1 = time.NewTicker(dur1 + dur2)
}

for  {
    select {
    case t := <-ticker1.C:
        once.Do(delayOnce)
        fmt.Println("ticker1:", t)
    case t := <-ticker2.C:
        fmt.Println("ticker2:", t)
    }

}