Merge pull request #10 from weberr13/set-field-with-unmarshaler

Add method to parse underlying type into object

decode/decode_test.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"testing"
+	"time"
 
 	. "github.com/smartystreets/goconvey/convey"
 	"github.com/weberr13/go-decode/decode"
@@ -94,6 +95,11 @@ type LivesInStruct struct {
 	LivesIn *RequiredBasicTypes
 }
 
+type TimedStruct struct {
+	Name string
+	UpdateTime *time.Time
+}
+
 func MyTestFactory(kind string) (interface{}, error) {
 	fm := map[string]func() interface{}{
 		"record":      NewRecord,
@@ -475,4 +481,17 @@ func TestDecodeNestedObject(t *testing.T) {
 		_, err := decode.UnmarshalJSONInto([]byte(b), &PetOwner{}, SchemaPathFactory)
 		So(err, ShouldNotBeNil)
 	})
+	Convey("Test parsing and decoding with underlying type", t, func() {
+		b := `{ "name": "john", "updateTime": "2019-10-21T14:56:28.292468-06:00" }`
+		i, err := decode.UnmarshalJSONInto([]byte(b), &TimedStruct{}, nil)
+		So(err, ShouldBeNil)
+		expTime, _ := time.Parse(time.RFC3339, "2019-10-21T14:56:28.292468-06:00")
+		So(i.(*TimedStruct), ShouldResemble, &TimedStruct{Name: "john", UpdateTime: &expTime})
+
+	})
+	Convey("Test parsing and decoding with incorrect underlying type", t, func() {
+		b := `{ "name": "john", "updateTime": "string" }`
+		_, err := decode.UnmarshalJSONInto([]byte(b), &TimedStruct{}, nil)
+		So(err, ShouldNotBeNil)
+	})
 }

decode/decoder.go

@@ -159,7 +159,11 @@ func DecodeInto(m map[string]interface{}, o interface{}, pf PathFactory) (interf
 			nV := reflect.New(ft)
 
 			if !vV.Type().ConvertibleTo(ft) {
-				return nil, fmt.Errorf("cannot convert value (%v) to field '%s' type\n", v, fldName)
+				err := parseAndSetField(fldName, field, nV, vV)
+				if err != nil {
+					return nil, err
+				}
+				continue
 			}
 			nV.Elem().Set(vV.Convert(ft))
 			field.Set(nV.Elem().Addr())
@@ -348,3 +352,23 @@ func UnmarshalJSONInto(b []byte, o interface{}, pf PathFactory) (interface{}, er
 	}
 	return DecodeInto(m, o, pf)
 }
+
+func parseAndSetField(path string, field, newField, val reflect.Value) error {
+	unmarshaler, ok := newField.Interface().(json.Unmarshaler)
+	if ok {
+		// marshal val back to []byte since it was converted to some underlying type (int/string)
+		valBytes, err := json.Marshal(val.Interface());
+		if err != nil {
+			return fmt.Errorf("Cannot convert value to []byte when attempting to set '%s': %s", path, err) 
+		}
+		// unmarshal valBytes back into newField object via the unmarshaler
+		err = unmarshaler.UnmarshalJSON(valBytes)
+		if err != nil {
+			return fmt.Errorf("Cannot unmarshal byte values for field '%s': %s", path, err)
+		}
+		// set field to the value unmarshaled into newField
+		field.Set(newField)
+		return nil
+	}
+	return fmt.Errorf("cannot convert value (%v) to field '%s' type", val, path)
+}