I have a function
func doStuff(inout *interface{}) {
...
}
the purpose of this function is to be able to treat a pointer of any type as input. But when I want to call it with a the pointer of a struct I have an error.
type MyStruct struct {
f1 int
}
When calling doStuff
ms := MyStruct{1}
doStuff(&ms)
I have
test.go:38: cannot use &ms (type *MyStruct) as type **interface {} in argument to doStuff
How can I cast &ms to be compatible with *interface{}?
There is no such thing as a "pointer to an interface" (technically, you can use one, but generally you don't need it).
As seen in "what is the meaning of interface{} in golang?", interface is a container with two words of data:
So remove the pointer, and doStuff will work just fine: the interface data will be &ms, your pointer:
func doStuff(inout interface{}) {
...
}
See this example:
ms := MyStruct{1}
doStuff(&ms)
fmt.Printf("Hello, playground: %v\n", ms)
Output:
Hello, playground: {1}
As newacct mentions in the comments:
Passing the pointer to the interface directly works because if
MyStructconforms to a protocol, then*MyStructalso conforms to the protocol (since a type's method set is included in its pointer type's method set).In this case, the interface is the empty interface, so it accepts all types anyway, but still.
MyStruct conforms to a protocol, then *MyStruct also conforms to the protocol (since a type's method set is included in its pointer type's method set). In this case, the interface is the empty interface, so it accepts all types anyway, but still.
reflect.TypeOf(&MyStruct{}).Elem() == reflect.TypeOf(MyStruct) See play.golang.org/p/DGb87RUZqJ