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nil_check_working.go
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| package main | |
| import ( | |
| "fmt" | |
| "reflect" | |
| ) | |
| type Animal interface { | |
| MakeSound() string | |
| } | |
| type Dog struct{} | |
| func (d *Dog) MakeSound() string { | |
| return "Bark" | |
| } | |
| type Cat struct{} | |
| func (c Cat) MakeSound() string { | |
| return "Meow" | |
| } | |
| func isNil(i interface{}) bool { | |
| return i == nil || reflect.ValueOf(i).IsNil() | |
| } | |
| func isNilFixed(i interface{}) bool { | |
| if i == nil { | |
| return true | |
| } | |
| switch reflect.TypeOf(i).Kind() { | |
| case reflect.Ptr, reflect.Map, reflect.Array, reflect.Chan, reflect.Slice: | |
| return reflect.ValueOf(i).IsNil() | |
| } | |
| return false | |
| } | |
| func isNilBetter(i Animal) bool { | |
| var ret bool | |
| switch i.(type) { | |
| case *Dog: | |
| v := i.(*Dog) | |
| ret = v == nil | |
| case Cat: | |
| ret = false | |
| } | |
| return ret | |
| } | |
| func main() { | |
| var d *Dog = nil | |
| var a Animal = d | |
| fmt.Println(isNilFixed(a)) | |
| var c Cat | |
| a = c | |
| fmt.Println(isNilFixed(a)) | |
| var m map[string] string | |
| fmt.Println(isNilFixed(m)) | |
| var s []string | |
| fmt.Println(isNilFixed(s)) | |
| var ch chan string | |
| fmt.Println(isNilFixed(ch)) | |
| } |
Thank you!
Thank you very much for your gist and for your post
Here below you can find my two cents
func myIsNil(i Animal) bool {
var ret bool
switch i.(type) {
case *Dog:
v := i.(*Dog)
ret = v == nil
case Cat:
ret = false
default:
ret = isNilFixed(i) // so isNilFixed() is called only if we forgot to implement some cases
// add some log to remember to add new cases to the switch to improve performance
}
return ret
}
Ciao,
Antonio
Thanks for the gist, but I found something weird in it and double-checked in the playground and the code isNilFixed would actually panic in the Array case, because arrays can not be nil. Can you confirm?
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