CODEWITHSUNDEEP
gocommand-line-interface
wayfare
wayfare

Reputation: 1850

How to exit from my go code using go routines and term ui

I recently started learning go and I am really impressed with all the features. I been playing with go routines and term-ui and facing some trouble. I am trying to exit this code from console after I run it but it just doesn't respond. If I run it without go-routine it does respond to my q key press event.

Any help is appreciated.

My code

package main

import (
    "fmt"
    "github.com/gizak/termui"
    "time"
    "strconv"
)

func getData(ch chan string) {
  i := 0
  for {
    ch <- strconv.Itoa(i)
    i++
    time.Sleep(time.Second)
    if i == 20 {
        break
    }
  }
}

func Display(ch chan string) {
  err := termui.Init()
  if err != nil {
    panic(err)
  }
  defer termui.Close()
  termui.Handle("/sys/kbd/q", func(termui.Event) {
    fmt.Println("q captured")
    termui.Close()
    termui.StopLoop()
  })

  for elem := range ch {
    par := termui.NewPar(elem)
    par.Height = 5
    par.Width = 37
    par.Y = 4
    par.BorderLabel = "term ui example with chan"
    par.BorderFg = termui.ColorYellow
    termui.Render(par)
  }
}

func main() {
  ch := make(chan string)
  go getData(ch)
  Display(ch)
}

Upvotes: 0

Views: 453

Answers (1)

RayfenWindspear
RayfenWindspear

Reputation: 6274

This is possibly the answer you are looking for. First off, you aren't using termui correctly. You need to call it's Loop function to start the Event loop so that it can actually start listening for the q key. Loop is called last because it essentially takes control of the main goroutine from then on until StopLoop is called and it quits.

In order to stop the goroutines, it is common to have a "stop" channel. Usually it is a chan struct{} to save memory because you don't ever have to put anything in it. Wherever you want the goroutine to possibly stop and shutoff (or do something else perhaps), you use a select statement with the channels you are using. This select is ordered, so it will take from them in order unless they block, in which case it tries the next one, so the stop channel usually goes first. The stop channel normally blocks, but to get it to take this path, simply close()ing it will cause this path to be chosen in the select. So we close() it in the q keyboard handler.

package main

import (
    "fmt"
    "github.com/gizak/termui"
    "strconv"
    "time"
)

func getData(ch chan string, stop chan struct{}) {
    i := 0
    for {
        select {
        case <-stop:
            break
        case ch <- strconv.Itoa(i):
        }
        i++
        time.Sleep(time.Second)
        if i == 20 {
            break
        }
    }
}

func Display(ch chan string, stop chan struct{}) {

    for {
        var elem string
        select {
        case <-stop:
            break
        case elem = <-ch:
        }
        par := termui.NewPar(elem)
        par.Height = 5
        par.Width = 37
        par.Y = 4
        par.BorderLabel = "term ui example with chan"
        par.BorderFg = termui.ColorYellow
        termui.Render(par)
    }
}

func main() {
    ch := make(chan string)
    stop := make(chan struct{})
    err := termui.Init()
    if err != nil {
        panic(err)
    }
    defer termui.Close()
    termui.Handle("/sys/kbd/q", func(termui.Event) {
        fmt.Println("q captured")
        close(stop)
        termui.StopLoop()
    })
    go getData(ch, stop)
    go Display(ch, stop)
    termui.Loop()
}

Upvotes: 1

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