How to invoke chaincode in Hyperledger fabric?

• Every chaincode program must implement the chaincode interface.
• The init method is called when a chaincode receives an instantiate or upgrade transaction so that the chaincode may perform any necessary initialization, including initialization of application state.
• The Invoke method is called in response to receiving an Invoke transaction to process transaction proposals.
• The other interface in the chaincode “shim” APIs is the ChaincodeStubInterface which is used to access and modify the ledger, and to make invocations between chaincodes.

Choosing a Location for the Code

For chaincode written in GO:
You may want to make sure that you have Go Programming Language installed and your system properly configured.

Now, you will want to create a directory for your chaincode application as a child directory of $GOPATH/src/.

To keep things simple, let’s use the following command:

mkdir -p $GOPATH/src/sacc && cd $GOPATH/src/sacc

Now, let’s create the source file that we’ll fill in with code:

touch sacc.go

Build & start the chaincode

docker exec -it chaincode bash

You should see the following:

root@d2629980e76b:/opt/gopath/src/chaincode#

Now, compile your chaincode:

cd sacc
go build

Now run the chaincode:

CORE_PEER_ADDRESS=peer:7052 CORE_CHAINCODE_ID_NAME=mycc:0 ./sacc

The chaincode is started with peer and chaincode logs indicating successful registration with the peer. Note that at this stage the chaincode is not associated with any channel. This is done in subsequent steps using the instantiate command.

Use the chaincode

Even though you are in --peer-chaincodedev mode, you still have to install the chaincode so the life-cycle system chaincode can go through its checks normally. This requirement may be removed in future when in --peer-chaincodedev mode.

We’ll leverage the CLI container to drive these calls.

docker exec -it cli bash
peer chaincode install -p chaincodedev/chaincode/sacc -n mycc -v 0
peer chaincode instantiate -n mycc -v 0 -c '{"Args":["a","10"]}' -C myc

Now issue an invoke to change the value of “a” to “20”.

peer chaincode invoke -n mycc -c '{"Args":["set", "a", "20"]}' -C myc

Finally, query a. We should see a value of 20.

peer chaincode query -n mycc -c '{"Args":["query","a"]}' -C myc