What Are the Benefits and Applications of Empty Structs in Go?

Empty Structs in Go: Their Purpose and Applications

Go offers a unique feature with empty structures (struct{}). These zero-sized structures possess distinct characteristics that make them valuable in various scenarios.

Benefits of Empty Structures

• Minimal Memory Footprint: Empty structs have a size of 0 bytes, making them the smallest building block in Go. This allows for memory conservation when storing large collections of these structures in slices or channels.
• Efficiency in Channels: By using empty structures in channels, you can notify about events without transmitting any additional information. This is both efficient and space-saving.
• Container for Methods: Empty structs can serve as containers for methods, enabling you to mock interfaces for testing purposes. They allow you to define methods without needing any actual data.
• Set Implementation: An empty struct can represent a set object in Go. By utilizing a map with keys of the desired set elements, you can effectively implement a set that consumes minimal memory space.
• Implementation of Interfaces through Receiver Methods: Empty structs play a role in implementing interfaces through receiver methods. They provide a way to specify methods without defining any data members.

Examples of Usage

• Notification in channels:

import "sync"

var wg sync.WaitGroup

func notify() {
    wg.Done()
}

func main() {
    wg.Add(1)
    go notify()
    wg.Wait()
}

• Mocking interfaces:

import (
    "fmt"
    "testing"
)

type SomeInterface interface {
    DoSomething()
}

type Empty struct{}

func (e Empty) DoSomething() {
    fmt.Println("Doing something")
}

func Test(t *testing.T) {
    var i SomeInterface = Empty{}
    i.DoSomething()
}

• Implementing sets:

type Set[T comparable] map[T]struct{}

func NewSet[T comparable](s []T) Set[T] {
    set := make(Set[T], len(s))
    for _, v := range s {
        set[v] = struct{}{}
    }
    return set
}

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