go - Returning an optional value and an error -

go - Returning an optional value and an error -

what's best signature function returns optional value , possible error?

for example:

func findcolor(name string) (rgb, error) { ... }

(the empty rgb value black, valid color, can't utilize infer no value found. assume error might come database connection.)

the 2 options seem best boolean homecoming value:

func findcolor(name string) (rgb, bool, error) { ... } c, ok, err := findcolor(myname) if !ok { ... } else if err != nil { ... } ...

or special error value:

var colornotfound = errors.new(...) func findcolor(name string) (rgb, error) { ... } c, err := findcolor(...) if err == colornotfound { ... } else if err != nil { ... } ...

(making special errors seems pain.)

what's idiomatic approach?

the convention in go homecoming (value, error) , if error != nil value (or may be) invalid.

if have special errors need (like io.eof) making specific error normal practice. 3rd illustration idiomatic, if want different colornotfound.

var colornotfound = errors.new(...) func findcolor(name string) (rgb, error) { // ... } c, err := findcolor(...) if err == colornotfound { // special if colornotfound... } else if err != nil { // other kind of error... }

go