Add Has

Author: mattn

jsonpointer.go

@@ -19,6 +19,32 @@ func parse(pointer string) ([]string, error) {
 	return tokens, nil
 }
 
+func Has(obj interface{}, pointer string) (rv bool, err error) {
+	defer func() {
+		if e := recover(); e != nil {
+			err = fmt.Errorf("Invalid JSON pointer: %q: %v", pointer, e)
+		}
+	}()
+	tokens, err := parse(pointer)
+	if err != nil {
+		return false, err
+	}
+
+	i := 0
+	v := reflect.ValueOf(obj)
+	if len(tokens) > 0 && tokens[0] != "" {
+		for i < len(tokens) {
+			token := tokens[i]
+			if n, err := strconv.Atoi(token); err == nil {
+				v = v.Elem().Index(n)
+			} else {
+				v = v.MapIndex(reflect.ValueOf(token))
+			}
+			i++
+		}
+	}
+	return true, nil
+}
 func Get(obj interface{}, pointer string) (rv interface{}, err error) {
 	defer func() {
 		if e := recover(); e != nil {

jsonpointer_test.go

@@ -6,6 +6,37 @@ import (
 	"testing"
 )
 
+var testHasCases = []struct {
+	json    string
+	pointer string
+	expect  bool
+	err     string
+}{
+	{`{"foo":[1,3,true]}`, `/foo/2`, true, ``},
+	{`{"foo":2}`, `/foo`, true, ``},
+	{`{"foo":[]}`, `/fooo`, false, ``},
+	{`{"foo":3.14}`, ``, false, `Invalid JSON pointer: ""`},
+}
+
+func TestHas(t *testing.T) {
+	for _, testcase := range testGetCases {
+		var obj interface{}
+		err := json.Unmarshal([]byte(testcase.json), &obj)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		value, err := Get(obj, testcase.pointer)
+		if err != nil {
+			if err.Error() != testcase.err {
+				t.Fatal(testcase.json, err)
+			}
+		} else if !reflect.DeepEqual(value, testcase.expect) {
+			t.Fatalf("Expected %v, but %v:", testcase.expect, value)
+		}
+	}
+}
+
 var testGetCases = []struct {
 	json    string
 	pointer string