liuxiran commented on pull request #1812:
URL: https://github.com/apache/apisix-dashboard/pull/1812#issuecomment-825440571
> Hi, @liuxiran
> In golang, you should distinguish `nil slice` and `empty slice`
>
> ```
> var x []*entity.Node
> ```
>
> is a nil slice.
>
> ```
> y := make([]*entity.Node, 0)
> ```
>
> is an empty slice. The length and value are 0.
> If you use printf or println to print them, the result is both "[]".
>
> In this situation, because the upstream.Nodes' type is interface{}.So it's
a little more complex.
> You can use
>
> ```
> reflect.ValueOf(upstream.Nodes).IsNil()
> ```
>
> to see the true value.
@starsz Thanks for your detailed explanation, after added
`reflect.ValueOf(upstream.Nodes).IsNil()` and debug again, I find out the
confusion before:
debug step:
1. create an upstream with no nodes
2. visit uptream page, call `GET /apisix/admin/upstreams`
3. config the upstream ,call `GET /apisix/admin/upstream/:id`
before the advice change, I got the logs:
after the advice change, I got the logs:
The conclusion is that:
the original `upstream.nodes` type got from etcd is `[]interface{}`, and it
is an empty slice,
it will be changed to type nodes , `[]*Node`, in FormatNodes `case
[]interface{}` when I visit upstream page(step2),
and the when I got the upstream info(step3), the data come from catch
instead of stroge, that is to say, in this scene, the `upstream.nodes` type is
already `[]*Node`.
so the advice will solve the problem.
Thanks again for all your help, then I will try to add related test cases
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