Chaincode HLF store variables with additional info - couchdb

Question

i am using a hlf system based on chaincode to show how smart contracts could be created.
Now i am stuck with (in my mind) a very easy problem i guess.
I want to store a data objects content as key-value pair on the chains couchDb state database.
I am doing this with a docker request looking like this:
COMMAND WRITE: docker exec -t Lane1_Zf4URs_cli peer chaincode invoke -o orderer.Zf4URs.com:7050 --tls --cafile /opt/gopath/src/github.com/hyperledger/fabric/peer/crypto/ordererOrganizations/Zf4URs.com/orderers/orderer.Zf4URs.com/msp/tlscacerts/tlsca.Zf4URs.com-cert.pem -C mychannel -n 9bc7cca8-1dcd-49b0-a25c-fb639a0403cf -c '{"Args":["set", "[D1]{P1}", "data4"]}'
So as you see my args are calling set method and store key="[Di]{P1}" value="data4" this is working fine with this "set" method.
func (s *SmartContract) set(stub shim.ChaincodeStubInterface, args []string) peer.Response {
if len(args) != 2 {
return shim.Error("Incorrect arguments. Expecting a key and a value")
}
err := stub.PutState(args[0], []byte(args[1]))
if err != nil {
return shim.Error("Failed to set asset: " + string(args[0]))
}
return shim.Success([]byte(args[1]))
// return args[1]
}
Now when looking at state dB this is the stored result:
{
"_id": "[D1]{P1}",
"_rev": "2-a74269cadec50f97d34d165d60235e34",
"~version": "8:0",
"_attachments": {
"valueBytes": {
"content_type": "application/octet-stream",
"revpos": 2,
"digest": "md5-2cRbxPYpSEbldj1mVovx8Q==",
"length": 5,
"stub": true
}
}
}
Now what i want to have is to store an additional value on this state db request.
Beside of "_id" (key) i want to have another field called "_executor" which should have a value "{P1}"
Should look like this:
{
"_id": "[D1]{P1}",
"_rev": "2-a74269cadec50f97d34d165d60235e34",
"_executor": "{P1}",
"~version": "8:0",
"_attachments": {
"valueBytes": {
"content_type": "application/octet-stream",
"revpos": 2,
"digest": "md5-2cRbxPYpSEbldj1mVovx8Q==",
"length": 5,
"stub": true
}
}
}
How can i do that?
What do i have to change on the docker request or on the set method?
Is this even possible?
Many thanks for help

Answer 1

This should work!
You have no constrains on the second argument (args[1]) in your smart contract. And since this is a string it's stored in one column and hence doesn't depend on the table structure.

Answer 2

I have updated my code.
I tried to use a struct and store this.
`type DataObject struct {
Name string
Executor string
Data []byte} func (s *SmartContract) set(stub shim.ChaincodeStubInterface, args []string) peer.Response {
if len(args) != 2 {
return shim.Error("Incorrect arguments. Expecting a key and a value")
}
p := DataObject{
Name: args[0],
Executor: "p1",
Data: []byte(args[1]),
}
str, err2 := json.Marshal(p)
if err2 != nil {
fmt.Println(err2)
}
fmt.Println(string(str))
if(args[1] == "data4"){
err := stub.PutState(args[0], str)
if err != nil {
return shim.Error("Failed to set asset: " + string(args[0]))
}
return shim.Success(str)
} else {
err := stub.PutState(args[0], []byte(args[1]))
if err != nil {
return shim.Error("Failed to set asset: " + string(args[0]))
}
return shim.Success([]byte(args[1]))
}}`
Now i can store executor but my data variable gets not stored as before. I need the digest so as before it should be _attachments: [valueBytes: ....digest:md5-xxx].
It looks like this:
couchDb-doc
{
"_id": "[D1]{P1}",
"_rev": "1-69be87268fs88s788668f8s766fnkushof7",
"Data": "ZGF0YTQ=",
"Executor": "P1",
"Name": "[D1]{P1}",
"_version": "3:0"
}