Merge pull request #52 from Liujingfang1/master

variable reference support

pkg/resource/resource.go

@@ -19,6 +19,7 @@ package resource
 
 import (
 	"encoding/json"
+	"fmt"
 
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/runtime"
@@ -109,3 +110,29 @@ func newUnstructuredFromObject(in runtime.Object) (*unstructured.Unstructured, e
 	err = out.UnmarshalJSON(marshaled)
 	return &out, err
 }
+
+func GetFieldValue(m map[string]interface{}, pathToField []string) (string, error) {
+	if len(pathToField) == 0 {
+		return "", fmt.Errorf("Field not found")
+	}
+
+	if len(pathToField) == 1 {
+		if v, found := m[pathToField[0]]; found {
+			if s, ok := v.(string); ok {
+				return s, nil
+			}
+			return "", fmt.Errorf("value at fieldpath is not of string type")
+		}
+		return "", fmt.Errorf("field at given fieldpath does not exist")
+	}
+
+	curr, rest := pathToField[0], pathToField[1]
+
+	v := m[curr]
+	switch typedV := v.(type) {
+	case map[string]interface{}:
+		return GetFieldValue(typedV, []string{rest})
+	default:
+		return "", fmt.Errorf("%#v is not expected to be a primitive type", typedV)
+	}
+}

pkg/resource/resource_test.go

@@ -0,0 +1,66 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package resource
+
+import (
+	"testing"
+)
+
+func TestGetFieldAsString(t *testing.T) {
+	m := map[string]interface{}{
+		"Kind": "Service",
+		"metadata": map[string]interface{}{
+			"labels": map[string]string{
+				"app": "application-name",
+			},
+			"name": "service-name",
+		},
+	}
+
+	tests := []struct {
+		pathToField   []string
+		expectedName  string
+		expectedError bool
+	}{
+		{
+			pathToField:   []string{"Kind"},
+			expectedName:  "Service",
+			expectedError: false,
+		},
+		{
+			pathToField:   []string{"metadata", "name"},
+			expectedName:  "service-name",
+			expectedError: false,
+		},
+		{
+			pathToField:   []string{"metadata", "non-existing-field"},
+			expectedName:  "",
+			expectedError: true,
+		},
+	}
+
+	for _, test := range tests {
+		s, err := GetFieldValue(m, test.pathToField)
+		if test.expectedError && err == nil {
+			t.Fatalf("should return error, but no error returned")
+		} else {
+			if test.expectedName != s {
+				t.Fatalf("Got:%s expected:%s", s, test.expectedName)
+			}
+		}
+	}
+}