add cache

cache.go

@@ -0,0 +1,15 @@
+package ds
+
+import (
+	"cloud.google.com/go/datastore"
+)
+
+// Cache interface
+type Cache interface {
+	Get(*datastore.Key, interface{}) error
+	GetMulti([]*datastore.Key, []interface{}) error
+	Set(*datastore.Key, interface{}) error
+	SetMulti([]*datastore.Key, []interface{}) error
+	Del(*datastore.Key) error
+	DelMulti([]*datastore.Key) error
+}

ds.go

@@ -11,6 +11,7 @@ import (
 // Client type
 type Client struct {
 	*datastore.Client
+	Cache Cache
 }
 
 // NewClient creates new ds client which wrap datastore client

get.go

@@ -9,6 +9,9 @@ import (
 
 // GetByKey retrieves model from datastore by key
 func (client *Client) GetByKey(ctx context.Context, key *datastore.Key, dst interface{}) error {
+	if client.Cache != nil && client.Cache.Get(key, dst) == nil {
+		return nil
+	}
 	err := client.Get(ctx, key, dst)
 	SetKey(key, dst)
 	if err != nil {

put.go

@@ -8,9 +8,16 @@ import (
 
 // PutModel puts a model to datastore
 func (client *Client) PutModel(ctx context.Context, src interface{}) error {
-	x := src.(KeyGetSetter)
-	_, err := client.Put(ctx, x.GetKey(), x)
-	return err
+	key := src.(KeyGetSetter).GetKey()
+	key, err := client.Put(ctx, key, src)
+	SetKey(key, src)
+	if err != nil {
+		return err
+	}
+	if client.Cache != nil {
+		client.Cache.Del(key)
+	}
+	return nil
 }
 
 // PutModels puts models to datastore
@@ -23,5 +30,8 @@ func (client *Client) PutModels(ctx context.Context, src interface{}) error {
 	}
 	keys, err := client.PutMulti(ctx, keys, src)
 	SetKeys(keys, src)
-	return err
+	if err != nil {
+		return err
+	}
+	return nil
 }

save.go

@@ -24,10 +24,7 @@ func beforeSave(src interface{}) {
 // if key was not set in model, will call NewKey
 func (client *Client) SaveModel(ctx context.Context, src interface{}) error {
 	beforeSave(src)
-
-	x := src.(KeyGetSetter)
-	key, err := client.Put(ctx, x.GetKey(), x)
-	x.SetKey(key)
+	err := client.PutModel(ctx, src)
 	if err != nil {
 		return err
 	}