Runtime error: assignment to entry in nil map
I am trying to generate a map and then convert that to a yaml file like this:
uid :
kasi:
cn: Chaithra
street: fkmp
nandan:
cn: Chaithra
street: fkmp
remya:
cn: Chaithra
street: fkmp
I think I am missing something important while creating the map. My code is below.
package main
import (
"fmt"
"gopkg.in/yaml.v2"
)
type T struct {
cn string
street string
}
func main() {
names := []string{"kasi", "remya", "nandan"}
m := make(map[string]map[string]T, len(names))
for _, name := range names {
//t := T{cn: "Chaithra", street: "fkmp"}
m["uid"][name] = T{cn: "Chaithra", street: "fkmp"}
}
fmt.Println(m)
y, _ := yaml.Marshal(&m)
fmt.Println(string(y))
//fmt.Println(m, names)
}
It is giving the following error:
panic: runtime error: assignment to entry in nil map
You have not initialized your inner map. Before your for loop you can add m["uid"] = make(map[string]T)
and then assign the name.
You should check if the map is nil and initialize one if it's nil inside the for loop:
if m["uid"] == nil {
m["uid"] = map[string]T{}
}
There is thing as per the error
assignment to entry in nil map
For nested maps when assign to the deep level key we needs to be certain that its outer key has value. Else it will say that the map is nil. For eg in your case
m := make(map[string]map[string]T, len(names))
m is a nested map which contains string
key with map[string]T
as value. And you are assign the value
m["uid"][name] = T{cn: "Chaithra", street: "fkmp"}
here you can see the m["uid"]
is nil
and we are stating it contains a value [name]
which is a key to nested value of type T
. So first you need to assign value to "uid" or initialise it as
m["uid"] = make(map[string]T)