🐛 Fixing a bug. about pointer package function (#230)

update:
1. UnwarpOr
2. UnwarpOrDefault
3. ExtractPointer

add:
1. UnwrapOr
2. IsNil

pointer/pointer.go

@@ -11,17 +11,24 @@ import (
 // Of returns a pointer to the value `v`.
 // Play: https://go.dev/play/p/HFd70x4DrMj
 func Of[T any](v T) *T {
+	if IsNil(v) {
+		return nil
+	}
 	return &v
 }
 
 // Unwrap returns the value from the pointer.
-// Play: https://go.dev/play/p/cgeu3g7cjWb
+//
+//	Play: https://go.dev/play/p/cgeu3g7cjWb
+//	Deprecated: Please use UnwrapOr
 func Unwrap[T any](p *T) T {
 	return *p
 }
 
 // UnwarpOr returns the value from the pointer or fallback if the pointer is nil.
-// Play: https://go.dev/play/p/mmNaLC38W8C
+//
+//	Play: https://go.dev/play/p/mmNaLC38W8C
+//	Deprecated: Please use UnwrapOr
 func UnwarpOr[T any](p *T, fallback T) T {
 	if p == nil {
 		return fallback
@@ -30,7 +37,9 @@ func UnwarpOr[T any](p *T, fallback T) T {
 }
 
 // UnwarpOrDefault returns the value from the pointer or the default value if the pointer is nil.
-// Play: https://go.dev/play/p/ZnGIHf8_o4E
+//
+//	Play: https://go.dev/play/p/ZnGIHf8_o4E
+//	Deprecated: Please use UnwrapOr
 func UnwarpOrDefault[T any](p *T) T {
 	var v T
 
@@ -40,9 +49,24 @@ func UnwarpOrDefault[T any](p *T) T {
 	return *p
 }
 
+// UnwrapOr returns the value from the pointer or fallback if the pointer is nil.
+func UnwrapOr[T any](p *T, fallback ...T) T {
+	if !IsNil(p) {
+		return *p
+	}
+	if len(fallback) > 0 {
+		return fallback[0]
+	}
+	var t T
+	return t
+}
+
 // ExtractPointer returns the underlying value by the given interface type
 // Play: https://go.dev/play/p/D7HFjeWU2ZP
 func ExtractPointer(value any) any {
+	if IsNil(value) {
+		return value
+	}
 	t := reflect.TypeOf(value)
 	v := reflect.ValueOf(value)
 
@@ -56,3 +80,8 @@ func ExtractPointer(value any) any {
 
 	return nil
 }
+
+// IsNil returns true if the given interface is nil or the underlying value is nil.
+func IsNil(i interface{}) bool {
+	return i == nil || (reflect.ValueOf(i).Kind() == reflect.Ptr && reflect.ValueOf(i).IsNil())
+}