what happend when golang convert struct to interface{} ? what is the cost?

Question

i'm confused about interface{} type,
how to build an interface{} object from Person struct?
if the struct is very big, the conversion cost whether is expensive

type Person struct {  
  name string  
  age  int  
} 

func test(any interface{}) {  

} 

func main() {  
    p := Person{"test", 11}
    // how to build an interface{} object from person struct? 
    // what is the cost? the field need copy?
    test(p) 
}

Answer 1

Interface{} is a type. It consists of two things : underlying type and underlying value. Size doesn't matter. Cost is that every time convert it or to it, you incur cost. One thing that size effect is value during copying from struct to interface underlying value. But this cost is similar to one you get when you assign to a struct or copy to a struct. The additional cost of interface isn't affected by size.

You don't need that function to convert, you can convert it like this:

func main() {
    p := Person{"test", 11}
    // how to build an interface{} object from person struct?
    // what is the cost? the field need copy?
    var v interface{}
    v = p    
}