golang de-reference a map

Question

Here is a sample code that creates a Map of string keys having value of bool.

myMap := make(map[string]bool)

myMap["Jan"] = true
myMap["Feb"] = false
myMap["Mar"] = true

After doing some operation on this map, I want to delete it. I don't want to use for loop to iterate through each key and delete.

If I do re-initialize myMap again (like following), does it de-references the original and subject to garbage collection?

myMap = make(map[string]bool)

I am very new to go, and was not sure if this is the right way of de-referencing. — Deepak Kumar
In Go "dereferencing" is the process of dereferencing a pointer to the value it points to, e.g. *p. There is no need to do "dereferencing to allow garbage collection". — Volker

Himanshu Himanshu · Accepted Answer · 2018-05-14T05:17:23

Golang FAQ on garbage collection:

Each variable in Go exists as long as there are references to it. If the compiler cannot prove that the variable is not referenced after the function returns, then the compiler must allocate the variable on the garbage-collected heap to avoid dangling pointer errors.

In case there are no references used for the current map it will be garbage collected by the language. But for deleting a map There is no process other than looping over it and delete the keys one by one. as

myMap := make(map[string]bool)
for k, _ := range myMap{
    delete(myMap, k)
}

If you re-initialze the map using make it will not going to de-reference the same it will clear the map but will not dereference it. If you check for its len it will become zero

package main

import (
    "fmt"
)

func main() {
    myMap := make(map[string]bool)

    myMap["Jan"] = true
    myMap["Feb"] = false
    myMap["Mar"] = true
    fmt.Println(len(myMap))
    myMap = make(map[string]bool)
    fmt.Println(len(myMap))

}

Along with that if you prints the address it points to same address.

fmt.Printf("address: %p \n", &myMap)
myMap = make(map[string]bool)
fmt.Printf("address: %p ", &myMap)

Playground Example

golang de-reference a map

1 Answers