Analysis of go for range pits and closure pits

  • 2020-06-23 00:38:42
  • OfStack

See the program:


package main
import (
  "fmt"
  "time"
)
func main() {
  str := []string{"I","like","Golang"}
  for _, v := range str{
   v += "good"
  }
  for k, v := range str{
   fmt.Println(k, v)
  }
  time.Sleep(1e9)
}

Results:

[

0 I
1 like
2 Golang

]

Think 1 think why.

Then look at:


package main
import (
  "fmt"
  "time"
)
func main() {
  str := []string{"I","like","Golang"}
  for k, v := range str{
   fmt.Println(&k, &v)
  }
  time.Sleep(1e9)
}

Results:

[

0xc000012050 0xc00000e1e0
0xc000012050 0xc00000e1e0
0xc000012050 0xc00000e1e0

]

Think 1 think why.

Then look at:


package main
import (
  "fmt"
  "time"
)
func main() {
  str := []string{"I","like","Golang"}
  for k, v := range str{
   str = append(str, "good")
   fmt.Println(k, v)
  }
  time.Sleep(1e9)
}

Results:

[

0 I
1 like
2 Golang

]

Think 1 think why.

Then look at:


package main
import (
  "fmt"
  "time"
)
func main() {
  str := []string{"I","like","Golang"}
  for k, v := range str{
   go func(i int, s string){
    fmt.Println(i, s, k, v)
   }(k, v)
  }
  time.Sleep(1e9)
}

Results:

[

0 I 2 Golang
1 like 2 Golang
2 Golang 2 Golang

]

Think 1 think why.

Finally:


package main
import (
  "fmt"
  "time"
)
func main() {
  str := []string{"I","like","Golang"}
  for k, v := range str{
   go func(i int, s string){
    fmt.Println(i, s, k, v)
   }(k, v)
   time.Sleep(1e9)
  }
  time.Sleep(5e9)
}

Results:

[

0 I 0 I
1 like 1 like
2 Golang 2 Golang

]

Think 1 think why.

Not much said.

conclusion


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