I believe that the *delete()* function doesn't actually remove items from
the map, only sets them to be ignored. i.e. The map data remains, but it
is skipped during the range iteration. Regardless, I think you need to
reconsider the logic of your approach to exiting the loop in the first
place. Some type of a conditional with a *break* statement would seem
better to me.
--
Kevin Powick
On Monday, 15 January 2018 22:00:30 UTC-5, sheepbao wrote:
>
> Thanks reply, I know *range expression is evaluated once before beginning
> the loop, *but I delete map in for statements also really affected the
> loop. why not set to nil can't affect real map.
>
> func mapTest() {
>
> m := map[int]int{1: 1, 2: 2}
>
> for k, v := range m {
>
> println(k, v)
>
> delete(m, 2)
>
> // m = nil
>
> }
>
> }
> // output:
> // 1 1
>
>
>
>
> On Tuesday, January 16, 2018 at 10:48:45 AM UTC+8, Kevin Powick wrote:
>>
>>
>>
>> On Monday, 15 January 2018 21:23:40 UTC-5, sheepbao wrote:
>>>
>>> I wrote this code, and why `map=nil` don't stop the loop?
>>> ```go
>>>
>>> func mapTest() {
>>>
>>> m := map[int]int{1: 1, 2: 2}
>>>
>>> for k, v := range m {
>>>
>>> println(k, v)
>>>
>>> m = nil
>>>
>>> }
>>>
>>> }
>>>
>>> ```
>>>
>>> output:
>>>
>>> 1 1
>>>
>>> 2 2
>>>
>>>
>>> I don't understand when I set `m = nil`, the loop is not stop. m
>>> doesn't seem to be affected.
>>>
>>
>> https://golang.org/ref/spec#For_statements
>>
>>
>> *The range expression is evaluated once before beginning the loop, with
>> one exception: if the range expression is an array or a pointer to an array
>> and at most one iteration variable is present, only the range expression's
>> length is evaluated; if that length is constant, by definition the range
>> expression itself will not be evaluated. *
>>
>>
>>
>> --
>> Kevin Powick
>>
>>
>>
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