CODEWITHSUNDEEP
gogoroutine
Yash Goel
Yash Goel

Reputation: 550

not able to fetch values from struct type channel in Go lang

With reference to this example, i want to add a pre-defined delay between job initialization and termination. I have stored the data i.e. jobid and waittime in map. Then i have copied the entire map in a channel of same struct type as map. But i am not able to fetch the map values in go routine calls. Please help me, I am new to Go.

package main

import "fmt"

type Vertex struct {
id, waitime int
}

var m = map[int]Vertex{
1:  {1, 1000},
2:  {2, 2000},
3:  {3, 1000},
4:  {4, 2000},
5:  {5, 1000},
6:  {6, 2000},
7:  {7, 1000},
8:  {8, 2000},
9:  {9, 1000},
10: {10, 2000},
}

func worker(w int, jobs <-chan Vertex, results chan<- int) {
for j := 1; j <= len(m); j++ {
    a, b := <-jobs.id, <-jobs.waitime
    fmt.Println("worker", w, "started job", a)
    //time.Sleep(time.Sleep(time.Duration(b)))
    fmt.Println("worker", w, "finished job", a)
    results <- j * 2
  }
}

func main() {
//n := 5
jobs := make(chan Vertex, 100)
results := make(chan int, 100)

for w := 1; w <= 5; w++ {
    go worker(w, jobs, results)
}
fmt.Println(len(m))
for j := 1; j <= len(m); j++ {
    jobs <- m[j]
}
//close(jobs)

for a := 1; a <= len(m); a++ {
    <-results
}
}

Upvotes: 1

Views: 1040

Answers (2)

abhink
abhink

Reputation: 9136

Couple of things are wrong with your code.

First, you can't access struct members directly off the channel. That is, this line is wrong:

a, b := <-jobs.id, <-jobs.waitime

jobs is a channel. It does not have any members called id or waittime. These are the members of the struct Vertex it's supposed to transfer. Change this line to:

job := <-jobs
a, b := job.id, job.waitime

But now, your code declares b but does not use it. To fix, uncomment the call to time.Sleep:

time.Sleep(time.Sleep(time.Duration(b))) !INCORRECT CALL

But this call is completely wrong. time.Sleep expects an argument of type time.Duration and returns nothing. To fix, make the following changes:

time.Sleep(time.Duration(b) * time.Millisecond)

This should get your code running.

Upvotes: 5

Nima Ghotbi
Nima Ghotbi

Reputation: 671

Change:

a, b := <-jobs.id, <-jobs.waitime

to:

job := <-jobs
a, b := job.id, job.waitime

jobs is a channel not a Vertex.

Upvotes: 1

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