Cast a struct pointer to interface pointer in Golang
casting, go, interface, pointers, struct
Solution
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:
- one word is used to point to a method table for the value’s underlying type,
- and the other word is used to point to the actual data being held by that value.
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 `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.
Problem
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{}`?