How can I pass a struct to a function as parameter?

Question

How can I pass a struct to function as a parameter in golang? There is my code:

package main  import (     "fmt" )  type MyClass struct {     Name string }  func test(class interface{}) {     fmt.Println(class.Name) }  func main() {      test(MyClass{Name: "Jhon"}) } 

when I run it, I am getting an error like this

# command-line-arguments /tmp/sandbox290239038/main.go:12: class.Name undefined (type interface {} has no field or method Name) 

there is play.golang.org fiddle address.

Answer 1

You're looking for;

func test(class MyClass) {     fmt.Println(class.Name) } 

As it stands the method recognizes class as some object which implements the empty interface (meaning in that scope it's fields and methods are completely unknown) which is why you get the error.

Your other option is something like this;

func test(class interface{}) {      if c, ok := class.(MyClass); ok { // type assert on it              fmt.Println(c.Name)      } } 

But there is no reason to in your example. It only makes sense if you're going to do a type switch or have multiple code paths that do different things based on the actual type of class.

Answer 2

Depending on your needs, you have (at least) two options:

1. Method on the struct type
2. Func that takes struct type as parameter

package main  import "fmt"  type MyClass struct {     Name string }  func main() {     cls := MyClass{Name: "Jhon"}      // Both calls below produce same result     cls.StructMethod()  // "Jhon"     FuncPassStruct(cls) // "Jhon" }  // Method on struct type func (class MyClass) StructMethod() {     fmt.Println(class.Name) }  // Function that takes struct type as the parameter func FuncPassStruct(class MyClass) {     fmt.Println(class.Name) } 

I'm sure others may provide some interface wizardry I'm forgetting.