how to get modification history of asset

Question

I am working on Bluemix and i want to fetch the asset modification history in Hyperledger fabric. i have gone around the documentation and i found stub.pushState(key,value_json) and stub.getState(key). I tried using this but realized that this can fetch only for latest key. But i want to fetch set of modification key and display it. i iterated on blocks using {peeraddress}/Block/getBlock/{Block} but i get decrypted info and cant display it.. How to do it?

Answer 1

You can use GetHistoryForKey() API as shown below:

historyIter, err := stub.GetHistoryForKey(key)

    if err != nil {
        errMsg := fmt.Sprintf("[ERROR] cannot retrieve history for key <%s>, due to %s", key, err)
        fmt.Println(errMsg)
        return shim.Error(errMsg)
    }

    for historyIter.HasNext() {
        modification, err := historyIer.Next()
        if err != nil {
            errMsg := fmt.Sprintf("[ERROR] cannot read record modification for key %s, id <%s>, due to %s", key, err)
            fmt.Println(errMsg)
            return shim.Error(errMsg)
        }
        fmt.Println("Returning information about", string(modification.Value))
    }

The link to the interface is : https://github.com/hyperledger/fabric/blob/release/core/chaincode/shim/interfaces.go#L164

Some functions in Query System Chaincode are:

const (
    GetChainInfo       string = "GetChainInfo"
    GetBlockByNumber   string = "GetBlockByNumber"
    GetBlockByHash     string = "GetBlockByHash"
    GetTransactionByID string = "GetTransactionByID"
    GetBlockByTxID     string = "GetBlockByTxID"
)

you can find more on: https://github.com/hyperledger/fabric/blob/release/core/scc/qscc/query.go#L40