[go-nuts] gotcha: don't take the address of a for-range loop variable

[buchanae]

https://play.golang.org/p/NnACN5fLPT3

I was taking the address of the for-loop variable ("&v" in the example 
above) and was surprised to find that all my items pointed the same 
address. I thought I had found most of the Golang gotchas by now, but this 
is a new one to me.

-A

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[go-nuts] gotcha: don't take the address of a for-range loop variable

[K Davidson]

You could also do: https://play.golang.org/p/zjNVeQNbCq5

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Re: [go-nuts] gotcha: don't take the address of a for-range loop variable

[Ian Lance Taylor]

On Sun, Jan 6, 2019 at 10:38 PM  wrote:
>
> https://play.golang.org/p/NnACN5fLPT3
>
> I was taking the address of the for-loop variable ("&v" in the example above) 
> and was surprised to find that all my items pointed the same address. I 
> thought I had found most of the Golang gotchas by now, but this is a new one 
> to me.

This is related to https://golang.org/doc/faq#closures_and_goroutines
.  But in general in a range loop the value is copied from the range
source to the loop variable.  Your sample code seems to think that the
loop variable is a reference to the slice element, but it's not; it's
a copy.  It's not surprising that the address of that copy, the loop
variable v, is always the same.

Ian

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Re: [go-nuts] gotcha: don't take the address of a for-range loop variable

[Steven Hartland]

Worth mentioning you don't need the second _ variable in range 
statements e.g. use:

    for i := range items {
   .
    }

vs:
    for i, _ := range items {
   .
    }
On 07/01/2019 02:24, bucha...@gmail.com wrote:

https://play.golang.org/p/NnACN5fLPT3

I was taking the address of the for-loop variable ("&v" in the example 
above) and was surprised to find that all my items pointed the same 
address. I thought I had found most of the Golang gotchas by now, but 
this is a new one to me.


-A
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