Merge pull request #10 from AlekSi/generics

Add generic functions

README.md

@@ -1,14 +1,15 @@
 # pointer
-[![GoDoc](https://godoc.org/github.com/AlekSi/pointer?status.svg)](https://godoc.org/github.com/AlekSi/pointer)
-[![Build Status](https://travis-ci.org/AlekSi/pointer.svg)](https://travis-ci.org/AlekSi/pointer)
 
-Go package pointer provides helpers to get pointers to values of built-in types.
+[![Go Reference](https://pkg.go.dev/badge/github.com/AlekSi/pointer.svg)](https://pkg.go.dev/github.com/AlekSi/pointer)
+
+Go package `pointer` provides helpers to convert between pointers and values of built-in
+(and, with Go 1.18+ generics, of any) types.
 
 ```
 go get github.com/AlekSi/pointer
 ```
 
-API is stable. [Documentation](http://godoc.org/github.com/AlekSi/pointer).
+API is stable. [Documentation](https://pkg.go.dev/github.com/AlekSi/pointer).
 
 ```go
 package motivationalexample

generic.go

@@ -0,0 +1,36 @@
+//go:build go1.18
+// +build go1.18
+
+package pointer
+
+// To returns a pointer to the passed value.
+func To[T any](t T) *T {
+	return &t
+}
+
+// ToOrNil returns a pointer to the passed value, or nil, if the passed value is a zero value.
+// If the passed value has `IsZero() bool` method (for example, time.Time instance),
+// it is used to determine if the value is zero.
+func ToOrNil[T comparable](t T) *T {
+	if z, ok := any(t).(interface{ IsZero() bool }); ok {
+		if z.IsZero() {
+			return nil
+		}
+		return &t
+	}
+
+	var zero T
+	if t == zero {
+		return nil
+	}
+	return &t
+}
+
+// Get returns the value from the passed pointer or the zero value if the pointer is nil.
+func Get[T any](t *T) T {
+	if t == nil {
+		var zero T
+		return zero
+	}
+	return *t
+}

generic_test.go

@@ -0,0 +1,33 @@
+//go:build go1.18
+// +build go1.18
+
+package pointer
+
+import (
+	"testing"
+	"time"
+)
+
+func TestGeneric(t *testing.T) {
+	var x time.Time
+	if *To(x) != x {
+		t.Errorf("*To(%v)", x)
+	}
+	if ToOrNil(x) != nil {
+		t.Errorf("ToOrNil(%v)", x)
+	}
+	if Get((*time.Time)(nil)) != x {
+		t.Errorf("Time(%v)", nil)
+	}
+
+	x = time.Date(2014, 6, 25, 12, 24, 40, 0, time.UTC)
+	if *To(x) != x {
+		t.Errorf("*To(%v)", x)
+	}
+	if *ToOrNil(x) != x {
+		t.Errorf("*ToOrNil(%v)", x)
+	}
+	if Get(&x) != x {
+		t.Errorf("Get(%v)", &x)
+	}
+}

go.mod

@@ -1,3 +1,3 @@
 module github.com/AlekSi/pointer
 
-go 1.11
+go 1.18

pointer.go

@@ -1,4 +1,4 @@
-// Package pointer provides helpers to get pointers to values of built-in types.
+// Package pointer provides helpers to convert between pointers and values of built-in (and, with generics, of any) types.
 package pointer // import "github.com/AlekSi/pointer"
 
 import (