On Mon, Feb 11, 2019 at 5:48 PM Slawomir Pryczek <slawek1...@gmail.com> wrote: > > Hi Guys, > > When looking at this code below, you can see that the function will get LAST > value of i which is incremented inside the loop, but t is somehow copied and > taken inside a function so closure is created and it is bound to current > value of t, so we'll have its current value in function. This is strange as t > and i is defined on the same code block level (t will be discarded at the > same time as i, after the loop). > > I always thought that t would need to be passed explicitly to goroutine to > retain current value (which i did). But why assigning value in a loop is > treated differently in this regard than a straight assignment? Any URL where > such "special cases" are documented? Isn't it kind of design flaw, because > this seem very confusing that loop is creating single value and simple > assignment is creating multiple copies? Maybe you consider changing this in > go2?
This is well-documented behavior. The first link I can find is: https://github.com/golang/go/wiki/CommonMistakes The common mistake is to think that the for-loop variable is captured as value in the closure. It is not, it is a reference, and the go-routine sees the value of the variable when it runs, not when it is created. > > https://play.golang.org/p/6vx_qDOk51g > > 10 1 > 10 0 > 10 9 > 10 8 > 10 7 > 10 6 > 10 5 > 10 4 > 10 3 > 10 2 > > > Thanks, > Slawomir. > > > ----- > package main > import ( > "fmt" > "time" > ) > > func main() { > for i := 0; i < 10; i++ { > t := i > go func() { > time.Sleep(time.Millisecond * 100) > fmt.Println(i, t) > }() > } > time.Sleep(time.Millisecond * 1000) > } > > > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
