adding documentation and examples to Generics

Author: symonk

README.md

@@ -33,6 +33,7 @@ all the examples `Run` functions sequentially in line with the table of contents
 * [19 - Methods](methods/main.go)
 * [20 - Interfaces](interfaces/main.go)
 * [21 - Struct Embedding](structembedding/main.go)
+* [22 - Generics](generics/main.go)
 * [34 - Timers](timers/main.go)
 * [35 - Tickers](tickers/main.go)
 * [36 - Worker Pools](workerpools/main.go)

generics/main.go

@@ -0,0 +1,72 @@
+package generics
+
+import "fmt"
+
+/*
+Genetics was added to golang for version `1.18`.  Generics can also be known as
+`type parameters`.
+*/
+func Run() {
+	genericStruct()
+	genericMapExample()
+	/*
+		When invoking generic functions, we can often rely on type inference.
+		We don't have to specify the types for K and V when calling `sliceOfMapKeys`
+		The go compiler can infer them for us.
+	*/
+	inferredGenericsExample()
+}
+
+func genericStruct() {
+	elements := []int{1, 2, 3, 4}
+	NewGenericStruct[int](elements...).Iterate()
+	other := []string{"A", "B", "C"}
+	NewGenericStruct[string](other...).Iterate()
+}
+
+func genericMapExample() {
+	hash := make(map[int]string)
+	hash[1] = "A"
+	hash[2] = "B"
+	hash[3] = "C"
+	for _, key := range sliceOfMapKeys[int, string](hash) {
+		fmt.Println(key)
+	}
+}
+
+func inferredGenericsExample() {
+	hash := make(map[string]int)
+	hash["foo"] = 10
+	hash["bar"] = 20
+	_ = sliceOfMapKeys(hash)
+}
+
+// A Generic function that returns a slice of its keys
+func sliceOfMapKeys[K comparable, V any](hash map[K]V) []K {
+	container := make([]K, 0)
+	// Ranging a map by default iterates the keys.
+	for key := range hash {
+		container = append(container, key)
+	}
+	return container
+}
+
+type GenericStruct[T any] struct {
+	elements []T
+}
+
+func NewGenericStruct[T any](elements ...T) *GenericStruct[T] {
+	store := make([]T, 0)
+	store = append(store, elements...)
+	return &GenericStruct[T]{
+		elements: store,
+	}
+
+}
+
+// Defining methods on generic types as normal
+func (g *GenericStruct[T]) Iterate() {
+	for _, element := range g.elements {
+		fmt.Println(element)
+	}
+}

main.go

@@ -9,6 +9,7 @@ import (
 	"github.com/symonk/learning-golang/constants"
 	"github.com/symonk/learning-golang/forloop"
 	"github.com/symonk/learning-golang/functions"
+	"github.com/symonk/learning-golang/generics"
 	"github.com/symonk/learning-golang/helloworld"
 	"github.com/symonk/learning-golang/ifelse"
 	"github.com/symonk/learning-golang/interfaces"
@@ -78,5 +79,6 @@ func buildMap() map[string]func() {
 	fnMap["methods"] = methods.Run
 	fnMap["interfaces"] = interfaces.Run
 	fnMap["structembedding"] = structembedding.Run
+	fnMap["generics"] = generics.Run
 	return fnMap
 }