Check for nil and nil interface in Go

Question

Currently I'm using this helper function to check for nil and nil interfaces

func isNil(a interface{}) bool {   defer func() { recover() }()   return a == nil || reflect.ValueOf(a).IsNil() } 

Since reflect.ValueOf(a).IsNil() panics if the value's Kind is anything other than Chan, Func, Map, Ptr, Interface or Slice, I threw in the deferred recover() to catch those.

Is there a better way to achieve this check? It think there should be a more straight forward way to do this.

Answer 1

See for example Kyle's answer in this thread at the golang-nuts mailing list.

In short: If you never store (*T)(nil) in an interface, then you can reliably use comparison against nil, no need to use reflection. On the other hand, assigning untyped nil to an interface is always OK.

Answer 2

If neither of the earlier options works for you, the best I could came up so far is:

if c == nil || (reflect.ValueOf(c).Kind() == reflect.Ptr && reflect.ValueOf(c).IsNil()) 

At least it detects (*T)(nil) cases.