<pre><code>// when passing in a schema.MultiError
func FormatErrForResp(err error) error {
fmt.Println(reflect.TypeOf(err)) // prints schema.MultiError
what, ok := err.(schema.MultiError)
fmt.Println(what) // prints "0 errors" (zero value for MultiError)
fmt.Println(ok) // prints false
switch v := err.(type) {
case schema.MultiError:
// do something
default:
// do something
}
}
</code></pre>
<p>Reflection shows that it's of type<code>schema.MultiError</code> but both the type switch and the type assertion are failing. It falls to the default case</p>
<hr/>**评论：**<br/><br/>iygwaz: <pre><p>Additional information: in the function where the error is first encountered, the type switch goes through the correct case:</p>
<pre><code>if err := schema.NewDecoder().Decode(dst, r.Form); err != nil {
switch err.(type) {
case schema.MultiError:
// passes through here (correct)
default:
//
}
return err
}
</code></pre></pre>titpetric: <pre><p>Please put a working sample on the <a href="https://play.golang.org" rel="nofollow">go playground</a>, it will make it easier for us to inspect what you have outside of this function.</p>
<p>Are you sure you're not using a pointer, and the case should be <code>case *schema.MultiError</code>?</p>
<p>Edit: here's my version of a <a href="https://play.golang.org/p/kBmONKpHUc9" rel="nofollow">working playground</a>, so I'm betting there's some pointer mixup from what I've seen dealing with type switches.</p></pre>
