| title | weight |
|---|---|
Generics |
650 |
The Go 1.18 release (February 2022) adds support for generics. In the following section, we will take a look at the new language feature but we will not cover every detail.
Imagine you implement a function contains to check wheter a certain item is in a list:
func contains(list []int, item int) bool {
for _, current := range list {
if current == item {
return true
}
}
return false
}The function above only works for slices of the type int. If you need the same logic for strings you have to implement a new function which would look exactly the same apart from the types in the function signature. If the function is in the same package you also have to choose a different name.
func containsString(list []string, item string) bool {
for _, current := range list {
if current == item {
return true
}
}
return false
}Since Go 1.18 we can write the contains function in a generic way:
package main
import "fmt"
func contains[T comparable](items []T, item T) bool {
for _, current := range items {
if item == current {
return true
}
}
return false
}
func main() {
numbers := []int{1,2,4,5}
fmt.Println(contains(numbers, 1))
fmt.Println(contains(numbers, 3))
names := []string{"bob", "alice"}
fmt.Println(contains(names, "alice"))
fmt.Println(contains(names, "eve"))
}
<!--output-->
true
false
true
falseIn this example we create a max function which returns the bigger of two values. To specify the constraint we use the Ordered interface from the constraints package:
package main
import (
"golang.org/x/exp/constraints"
)
func max[T constraints.Ordered](a, b T) T {
if a > b {
return a
}
return b
}
func main() {
fmt.Println(max(13, 42))
fmt.Println(max(3.14, 2.71))
}
<!--output-->
42
3.14We can also use generics to parametrize structs:
type LinkedList[T any] struct {
head *Node[T]
}
type Node[T any] struct {
item T
next *Node[T]
}Official Go resources about the topic:
- An Introduction To Generics
- Tutorial: Getting started with generics
- When To Use Generics
- Type Parameters Proposal
Other blog posts about the topic: