Use a interator propeties in a cunston type

Question

I was writing Go code where I created a type using base map [string] int and I need to create a method that returns a map, reversing key and value. I started writing the code, but I can't iterate the type I created.

So far I've made the following code:

package constants

type Month map[string]int;

// LongMonth is a relationship with string and date value (int)
var LongMonth = Month{
    "Janary":1,
    "February":2,
    "March":3,
    "April":4, 
    "May":5,
    "June": 6,
    "July": 7,
    "August": 8,
    "September": 9,
    "Octuber": 10,
    "Novenber": 11,
    "Decenber": 12,
}

// ShortMonth is a relationship with a resume string and date value (int)
var ShortMonth = Month{
    "Jan":1,
    "Feb":2,
    "Mar":3,
    "Apr":4, 
    "May":5,
    "Jun": 6,
    "Jul": 7,
    "Aug": 8,
    "Sep": 9,
    "Oct": 10,
    "Nov": 11,
    "Dec": 12,
}

func (m* Month) Reverse() map[int]string {
    n:=make(map[int]string);
    for k, v := range m {
        n[v] = k
    }
    return n
};
// LongMonthReverse is a relationship with string and date value (int)
// var LongMonthReverse = reverseMonth(LongMonth);
// ShortMonthReverse is a relationship with string and date value (int)
// var ShortMonthReverse = reverseMonth(ShortMonth);

i need function Reverse return the revers emonth. Ex: month = {"Jan": 1..."Dec": 12} and month.Reverse() returns {1: "Jan"....12: "Dec"}

Answer 1

You can't iterate over a pointer either change the method interface of func (m* Month) Reverse() map[int]string to func (m Month) Reverse() map[int]string or you need to use *m inside of Reverse()

package main

import "fmt"


type Month map[string]int

// LongMonth is a relationship with string and date value (int)
var LongMonth = Month{
    "Janary":1,
    "February":2,
    "March":3,
    "April":4,
    "May":5,
    "June": 6,
    "July": 7,
    "August": 8,
    "September": 9,
    "Octuber": 10,
    "Novenber": 11,
    "Decenber": 12,
}

// ShortMonth is a relationship with a resume string and date value (int)
var ShortMonth = Month{
    "Jan":1,
    "Feb":2,
    "Mar":3,
    "Apr":4,
    "May":5,
    "Jun": 6,
    "Jul": 7,
    "Aug": 8,
    "Sep": 9,
    "Oct": 10,
    "Nov": 11,
    "Dec": 12,
}

func (m* Month) Reverse() map[int]string {
    n:=make(map[int]string)
    // this is the fix
    for k, v := range *m {
        n[v] = k
    }
    return n
}


func main() {
  fmt.Println(ShortMonth.Reverse())
}