CODEWITHSUNDEEP
go
Test admin
Test admin

Reputation: 731

Nested map creation in golang

I need to create a map as shown below:

package main

import "fmt"

func main() {   
   var data = map[string]interface{}{}  
   data["name"] = "User"    
   data["info"] = map[string]string{}   
   data["info"]["email"] = "[email protected]"  
   fmt.Println(data)
}

I am trying to create nested maps, but I am getting an error as shown below:

# command-line-arguments./interface.go:9: invalid operation: data["info"]["email"] (type interface {} does not support indexing)

Please provide solution to fix this error. Thanks in advance.

Upvotes: 2

Views: 4607

Answers (2)

Himanshu
Himanshu

Reputation: 12675

According to Golang Laws of Reflection

A variable of interface type stores a pair: the concrete value assigned to the variable, and that value's type descriptor. To be more precise, the value is the underlying concrete data item that implements the interface and the type describes the full type of that item

That's why we needs to type assert map[string]string to get the underlying value of map[string]interface{}

You also might wants to look at this post

For an example you can loop on maps they have indexes. But interface act like a wrapper around type T storing the value and its type. They don't have indexes as the error said.

Upvotes: 0

mu is too short
mu is too short

Reputation: 434665

Your data:

var data = map[string]interface{}{}

is a map from string to interface{} so data["info"] is just an interface{} until you assert its type as map[string]string:

data["info"].(map[string]string) // Now you have a map[string]string

Once you have a map[string]string, you can index it as desired:

data["info"].(map[string]string)["email"] = "[email protected]"

https://play.golang.org/p/yuyAN9FRCxc

Upvotes: 4

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