Added sort method to ContractAttributes array

pkg/core/blockchain.go

@@ -5,6 +5,6 @@ type Blockchain interface {
 	SubscribeToBlocks(blocks chan Block)
 	StartListening()
 	StopListening()
-	GetContractAttributes(contractHash string) ([]ContractAttribute, error)
+	GetContractAttributes(contractHash string) (ContractAttributes, error)
 	GetContractStateAttribute(contractHash string, attributeName string) (*string, error)
 }

pkg/core/watched_contract.go

@@ -9,3 +9,16 @@ type ContractAttribute struct {
 	Name string
 	Type string
 }
+
+type ContractAttributes []ContractAttribute
+
+func (s ContractAttributes) Len() int {
+	return len(s)
+}
+func (s ContractAttributes) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
+
+func (s ContractAttributes) Less(i, j int) bool {
+	return s[i].Name < s[j].Name
+}