Creating map with empty values

I need to use a map for keys only, I don't need to store values. So I declared a map like this:

map

modified_accounts:=make(map[int]struct)


The idea is to use empty struct because it doesn't consume storage.

However, when I tried to add an entry to the map,

modified_accounts[2332]=struct


I got a compile error:

./blockchain.go:291:28: type struct is not an expression


How do I add an empty key and no value to the map ?

struct

struct

2 Answers
2

You can do it declaring a empty variable

var Empty struct

func foo()
modified_accounts := make(map[int]struct)
modified_accounts[2332] = Empty
fmt.Println(modified_accounts)



Or creating a new struct every time

func bar()
modified_accounts := make(map[int]struct)
modified_accounts[2332] = struct
fmt.Println(modified_accounts)



To create a empty struct you should use struct

struct

struct

The error is exactly what you see in the below line :

./blockchain.go:291:28: type struct is not an expression

An expression is something that evaluates to something (something that has a value), struct is a type, and your statement is trying to assign a type(right) to a map's key's value, a variable(left)

evaluates to something

struct

What you need is to create a variable of this type, and assign that variable to the map's key as a value.

Either by using :

var x struct
modified_accounts[2332] = x


or

modified_accounts[2332] = struct


In either of the above way, you are creating a value of type struct, and assigning that value to the map's key.

struct

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