add function to_object to parse nested json string

api_test.go

@@ -42,3 +42,14 @@ func TestInvalidMustCompilePanics(t *testing.T) {
 	}()
 	MustCompile("not a valid expression")
 }
+
+func TestFunctionToObject(t *testing.T) {
+	assert := assert.New(t)
+	var j = []byte(`{"name":"John","test":{"js":"{\"age\": 26, \"city\": \"BeiJin\"}"},"nested_json":"{\"age\": 25, \"city\": \"NewYork\"}"}`)
+	var d interface{}
+	err := json.Unmarshal(j, &d)
+	assert.Nil(err)
+	result, err := Search("[name,to_object(test.js).city,to_object(nested_json).city]", d)
+	assert.Nil(err)
+	assert.Equal([]interface{}{"John", "BeiJin", "NewYork"}, result)
+}

functions.go

@@ -318,6 +318,13 @@ func newFunctionCaller() *functionCaller {
 			},
 			handler: jpfNotNull,
 		},
+		"to_object": {
+			name: "to_object",
+			arguments: []argSpec{
+				{types: []jpType{jpString}},
+			},
+			handler: jpfToObject,
+		},
 	}
 	return caller
 }
@@ -839,3 +846,13 @@ func jpfNotNull(arguments []interface{}) (interface{}, error) {
 	}
 	return nil, nil
 }
+
+func jpfToObject(arguments []interface{}) (interface{}, error) {
+	v := arguments[0].(string)
+	var obj interface{}
+	err := json.Unmarshal([]byte(v), &obj)
+	if err != nil {
+		return nil, errors.New("invalid json string")
+	}
+	return obj, nil
+}