How do I write a function for multiple types in Golang?
go, hypermedia, inheritance, reflection
Solution
I am not sure to understand what you are trying to do, but with reflection, you can see if a field exists or not and then do something with it.
Example derived from the 'laws of reflection' article (http://blog.golang.org/laws-of-reflection). Play: http://play.golang.org/p/neU3j2MYvz
package main
import (
"fmt"
"reflect"
)
type T1 struct {
A int
B string
}
type T2 struct {
A int
}
func fct(i interface{}) {
s := reflect.ValueOf(i).Elem()
typeOfT := s.Type()
for i := 0; i < s.NumField(); i++ {
f := s.Field(i)
if typeOfT.Field(i).Name == "B" {
fmt.Printf("I am %s and I have a field B: %s\n", typeOfT.Name(), f.Interface())
}
}
}
func main() {
t1 := T1{23, "skidoo"}
t2 := T2{23}
fct(&t1)
fct(&t2)
}
Problem
I'm trying to write a helper function that can take in different custom Types in Golang, but I can't figure out how to do it exactly the way I want. Here's the situation (incidentally, I'm building an API that returns JSON objects implementing HAL protocol. This just means that resources and relationships are returned as links and not simply ID'). I have a number of models in my app, such as Student, Principal, School, etc... Each of these models has many fields, some same, some different. Ideally, I'd like a function that can iterate through the fields of a struct, and change another field in the struct. The big challenge is that these structs can be of type Student, Principal, School, etc... Models: ``` type Person struct { halgo.Links Id bson.ObjectId Firstname string Lastname string Email string } type Student struct { Person `bson:",inline"` School mgo.DBRef } type School struct { Id bson.ObjectId Address []string Name string Description string } ``` Then, I'd like a function that can basically take any of these structs, iterate through the fields (using `reflect`), and do something with each field. I've tried a function that takes `interface{}` but the problem is you have to type-assert the argument to have access to any of the fields. And even once you have that, you'll still have to write individual functions for each type/model anyways.: ``` func GenerateLinksHelper(m interface{}) { ... } ``` Ultimately, I'm trying to find a way to write a function that takes in a somewhat arbitrary struct and perform operations on fields that may or may not be there.