support pointer to object slice

builder.go

@@ -13,7 +13,8 @@ func makeBuilder(t reflect.Type) (builder, error) {
 	case reflect.Struct:
 		return makeStructBuilder(t)
 	case reflect.Ptr:
-		if t.Elem().Kind() != reflect.Struct {
+		if t.Elem().Kind() != reflect.Struct &&
+			t.Elem().Kind() != reflect.Slice {
 			return makePrimitiveBuilder(t)
 		}
 		return makePointerBuilder(t)

format_test.go

@@ -367,6 +367,19 @@ func TestFormat(t *testing.T) {
 			format: "foo",
 			output: `[{"foo":1}]`,
 		},
+		{
+			src: &[]struct {
+				Foo int `json:"foo"`
+				Bar int `json:"bar"`
+			}{
+				{
+					Foo: 1,
+					Bar: 2,
+				},
+			},
+			format: "foo",
+			output: `[{"foo":1}]`,
+		},
 		{
 			src: struct {
 				Foo []int `json:"foo"`
@@ -400,7 +413,7 @@ func TestFormat(t *testing.T) {
 		},
 	}
 	for i, tt := range tests {
-		t.Run(fmt.Sprintf("test #%d", i), func(t *testing.T) {
+		t.Run(fmt.Sprintf("test #%d %s %s", i, tt.format, tt.output), func(t *testing.T) {
 			f := NewFormatter()
 			var fields []string
 			if tt.format != "" {

pointer.go

@@ -1,6 +1,7 @@
 package dynjson
 
 import (
+	"errors"
 	"reflect"
 )
 
@@ -25,7 +26,7 @@ func (f *pointerFormatter) format(src reflect.Value) (reflect.Value, error) {
 
 type pointerBuilder struct {
 	t    reflect.Type
-	elem *structBuilder
+	elem builder
 }
 
 func (b *pointerBuilder) build(fields []string, prefix string) (formatter, error) {
@@ -37,7 +38,16 @@ func (b *pointerBuilder) build(fields []string, prefix string) (formatter, error
 }
 
 func makePointerBuilder(t reflect.Type) (*pointerBuilder, error) {
-	eb, err := makeStructBuilder(t.Elem())
+	var eb builder
+	var err error
+	if t.Elem().Kind() == reflect.Struct {
+		eb, err = makeStructBuilder(t.Elem())
+	} else if t.Elem().Kind() == reflect.Slice {
+		eb, err = makeSliceBuilder(t.Elem())
+	} else {
+		return nil, errors.New("unable to handle this type")
+	}
+
 	if err != nil {
 		return nil, err
 	}

slice.go

@@ -20,7 +20,9 @@ func (f *sliceFormatter) format(src reflect.Value) (reflect.Value, error) {
 		}
 		dst.Index(i).Set(dv)
 	}
-	return dst, nil
+	dstAddr := reflect.New(f.t).Elem()
+	dstAddr.Set(dst)
+	return dstAddr, nil
 }
 
 type sliceBuilder struct {