Print an array of empty interfaces in golang?

I have a struct with a field of the form field []interface{}. If I print the field, I get back a pointer reference. If I try to dereference the field, I get an error "invalid indirect".

The code is below:

type MyType struct {
   field []interface{}
}
myType := //create a MyType. Field is just an array of numbers
println(myType.field) // prints a pointer reference, ex: [1/1]0xc420269aa0
println(*(myType.field)) // doesn't compile

How do I print the values in myType.field?

The answer is to loop through the array, or even better, use fmt.Println.

func dump(items []interface{}) {
 for i := 0; i < len(items); i++ {
	fmt.Println(items[i])
   }
}
// OR
fmt.Println(items)

Array interfaces can be printed as follows

questionSet := []interface{}{} 

// ... code to fillup the question set

fmt.Printf("%t", questionSet)

and here is the result

[%!t(*domain.Question=&{First Economics question 3 
[{Economics option 1 for student false} 
{Economics option 2 for student false} 
{Economics option 3 for student true} 
{Economics option 4 for student false}] 
[{Economics first topic} {Economics second topic}]}) 

%!t(*domain.Question=&{second Question 4 
[{Qs2 Option 1 for student false} 
{Qs2 Option 2 for student false} 
{Qs2 Option 3 for student false} 
{Qs2 Option 4 for student false}] 
[{third topic} {fourth topic}]})]

The output here is not very pretty but at least you can see the result and extract your relevant information for further process.

In the above result domain.Question is a struct and here is the complete struct for your reference. Hope this will help you to understand better.

type Question struct {
	Questions string            `json:"questions,omitempty" bson:"questions"`
	Marks     string            `json:"marks,omitempty" bson:"marks"`
	Options   []QuestionOptions `json:"options,omitempty" bson:"options"`
	Topics    []QuestionTopic   `json:"topics,omitempty" bson:"topics"`
}

type QuestionOptions struct {
	Option  string `json:"option" bson:"option"`
	Correct bool   `json:"correct" bson:"correct"`
}

type QuestionTopic struct {
	Topic string `json:"topic" bson:"topic"`
}

Consider that the verb %t is designed to print boolean (see the doc overview at https://golang.org/pkg/fmt/), as such, while using it to dump the content of a value works as of today, it is not the behavior intended by go authors, and as such, this behavior might change in the future.

Peace,

another way you could use

https://play.golang.org/p/4lLQ4Gb2S0m

package main

import (
	"encoding/json"
	"fmt"
)

func main() {
	fmt.Println(dump(new(bool)))
	fmt.Println(dump([]interface{}{new(bool), new(string)}))
}

func dump(x interface{}) string {
	json, err := json.MarshalIndent(x, "", "  ")
	if err != nil {
		panic(err)
	}

	return string(json)
}
// Outputs:
// false
// [
//   false,
//   ""
// ]