// Transaction queries another chaincode and updates its own state
func (t *SimpleChaincode) invoke(stub *shim.ChaincodeStub, args []string) ([]byte, error) {
var sum string // Sum entity
var Aval, Bval, sumVal int // value of sum entity - to be computed
var err error
if len(args) != 3 {
return nil, errors.New("Incorrect number of arguments. Expecting 3")
}
chaincodeUrl := args[0] // Expecting "github.com/openblockchain/obc-peer/openchain/example/chaincode/chaincode_example02"
chaincodeVersion := args[1] // Expecting "0.0.1"
sum = args[2]
// Query chaincode_example02
f := "query"
queryArgs := []string{"a"}
response, err := stub.QueryChaincode(chaincodeUrl, chaincodeVersion, f, queryArgs)
if err != nil {
errStr := fmt.Sprintf("Failed to query chaincode. Got error: %s", err.Error())
fmt.Printf(errStr)
return nil, errors.New(errStr)
}
Aval, err = strconv.Atoi(string(response))
if err != nil {
errStr := fmt.Sprintf("Error retrieving state from ledger for queried chaincode: %s", err.Error())
fmt.Printf(errStr)
return nil, errors.New(errStr)
}
queryArgs = []string{"b"}
response, err = stub.QueryChaincode(chaincodeUrl, chaincodeVersion, f, queryArgs)
if err != nil {
errStr := fmt.Sprintf("Failed to query chaincode. Got error: %s", err.Error())
fmt.Printf(errStr)
return nil, errors.New(errStr)
}
Bval, err = strconv.Atoi(string(response))
if err != nil {
errStr := fmt.Sprintf("Error retrieving state from ledger for queried chaincode: %s", err.Error())
fmt.Printf(errStr)
return nil, errors.New(errStr)
}
// Compute sum
sumVal = Aval + Bval
// Write sumVal back to the ledger
err = stub.PutState(sum, []byte(strconv.Itoa(sumVal)))
if err != nil {
return nil, err
}
fmt.Printf("Invoke chaincode successful. Got sum %d\n", sumVal)
return []byte(strconv.Itoa(sumVal)), nil
}
// Query callback representing the query of a chaincode
func (t *SimpleChaincode) Query(stub *shim.ChaincodeStub, function string, args []string) ([]byte, error) {
if function != "query" {
return nil, errors.New("Invalid query function name. Expecting \"query\"")
}
var sum string // Sum entity
var Aval, Bval, sumVal int // value of sum entity - to be computed
var err error
// Can query another chaincode within query, but cannot put state or invoke another chaincode (in transaction context)
if len(args) != 3 {
return nil, errors.New("Incorrect number of arguments. Expecting 3")
}
chaincodeUrl := args[0] // Expecting "github.com/openblockchain/obc-peer/openchain/example/chaincode/chaincode_example02"
chaincodeVersion := args[1] // Expecting "0.0.1"
sum = args[2]
// Query chaincode_example02
f := "query"
queryArgs := []string{"a"}
response, err := stub.QueryChaincode(chaincodeUrl, chaincodeVersion, f, queryArgs)
if err != nil {
errStr := fmt.Sprintf("Failed to query chaincode. Got error: %s", err.Error())
fmt.Printf(errStr)
return nil, errors.New(errStr)
}
Aval, err = strconv.Atoi(string(response))
if err != nil {
errStr := fmt.Sprintf("Error retrieving state from ledger for queried chaincode: %s", err.Error())
fmt.Printf(errStr)
return nil, errors.New(errStr)
}
queryArgs = []string{"b"}
response, err = stub.QueryChaincode(chaincodeUrl, chaincodeVersion, f, queryArgs)
if err != nil {
errStr := fmt.Sprintf("Failed to query chaincode. Got error: %s", err.Error())
fmt.Printf(errStr)
return nil, errors.New(errStr)
}
Bval, err = strconv.Atoi(string(response))
if err != nil {
errStr := fmt.Sprintf("Error retrieving state from ledger for queried chaincode: %s", err.Error())
fmt.Printf(errStr)
return nil, errors.New(errStr)
}
// Compute sum
sumVal = Aval + Bval
fmt.Printf("Query chaincode successful. Got sum %d\n", sumVal)
jsonResp := "{\"Name\":\"" + sum + "\",\"Value\":\"" + strconv.Itoa(sumVal) + "\"}"
fmt.Printf("Query Response:%s\n", jsonResp)
return []byte(strconv.Itoa(sumVal)), nil
}