support generics

go.mod

@@ -1,6 +1,6 @@
 module github.com/ake-persson/mapslice-json
 
-go 1.16
+go 1.18
 
 require (
 	github.com/client9/misspell v0.3.4 // indirect

mapslice.go

@@ -8,17 +8,18 @@ import (
 )
 
 // MapItem representation of one map item.
-type MapItem struct {
-	Key, Value interface{}
-	index      uint64
+type MapItem[V any] struct {
+	Key   string
+	Value V
+	index uint64
 }
 
 // MapSlice of map items.
-type MapSlice []MapItem
+type MapSlice[V any] []MapItem[V]
 
-func (ms MapSlice) Len() int           { return len(ms) }
-func (ms MapSlice) Less(i, j int) bool { return ms[i].index < ms[j].index }
-func (ms MapSlice) Swap(i, j int)      { ms[i], ms[j] = ms[j], ms[i] }
+func (ms MapSlice[V]) Len() int           { return len(ms) }
+func (ms MapSlice[V]) Less(i, j int) bool { return ms[i].index < ms[j].index }
+func (ms MapSlice[V]) Swap(i, j int)      { ms[i], ms[j] = ms[j], ms[i] }
 
 var indexCounter uint64
 
@@ -28,12 +29,12 @@ func nextIndex() uint64 {
 }
 
 // MapItem as a string.
-func (mi MapItem) String() string {
+func (mi MapItem[V]) String() string {
 	return fmt.Sprintf("{%v %v}", mi.Key, mi.Value)
 }
 
 // MarshalJSON for map slice.
-func (ms MapSlice) MarshalJSON() ([]byte, error) {
+func (ms MapSlice[V]) MarshalJSON() ([]byte, error) {
 	buf := &bytes.Buffer{}
 	buf.Write([]byte{'{'})
 	for i, mi := range ms {
@@ -52,21 +53,21 @@ func (ms MapSlice) MarshalJSON() ([]byte, error) {
 }
 
 // UnmarshalJSON for map slice.
-func (ms *MapSlice) UnmarshalJSON(b []byte) error {
-	m := map[string]MapItem{}
+func (ms *MapSlice[V]) UnmarshalJSON(b []byte) error {
+	m := map[string]MapItem[V]{}
 	if err := json.Unmarshal(b, &m); err != nil {
 		return err
 	}
 	for k, v := range m {
-		*ms = append(*ms, MapItem{Key: k, Value: v.Value, index: v.index})
+		*ms = append(*ms, MapItem[V]{Key: k, Value: v.Value, index: v.index})
 	}
 	sort.Sort(*ms)
 	return nil
 }
 
 // UnmarshalJSON for map item.
-func (mi *MapItem) UnmarshalJSON(b []byte) error {
-	var v interface{}
+func (mi *MapItem[V]) UnmarshalJSON(b []byte) error {
+	var v V
 	if err := json.Unmarshal(b, &v); err != nil {
 		return err
 	}

mapslice_test.go

@@ -7,10 +7,10 @@ import (
 )
 
 func TestMarshal(t *testing.T) {
-	ms := MapSlice{
-		MapItem{Key: "abc", Value: 123},
-		MapItem{Key: "def", Value: 456},
-		MapItem{Key: "ghi", Value: 789},
+	ms := MapSlice[int]{
+		MapItem[int]{Key: "abc", Value: 123},
+		MapItem[int]{Key: "def", Value: 456},
+		MapItem[int]{Key: "ghi", Value: 789},
 	}
 
 	b, err := json.Marshal(ms)
@@ -27,18 +27,18 @@ func TestMarshal(t *testing.T) {
 }
 
 func TestMarshalError(t *testing.T) {
-	ms := MapSlice{
-		MapItem{Key: "abc", Value: make(chan int)},
+	ms := MapSlice[chan int]{
+		MapItem[chan int]{Key: "abc", Value: make(chan int)},
 	}
 
-	e := "json: error calling MarshalJSON for type mapslice.MapSlice: json: unsupported type: chan int"
+	e := "json: error calling MarshalJSON for type mapslice.MapSlice[chan int]: json: unsupported type: chan int"
 	if _, err := json.Marshal(ms); err != nil && e != err.Error() {
 		t.Errorf("expected: %s\ngot: %v", e, err)
 	}
 }
 
 func TestUnmarshal(t *testing.T) {
-	ms := MapSlice{}
+	ms := MapSlice[int]{}
 	if err := json.Unmarshal([]byte("{\"abc\":123,\"def\":456,\"ghi\":789}"), &ms); err != nil {
 		t.Fatal(err)
 	}