package main
import (
"fmt"
"github.com/hyperledger/fabric-contract-api-go/contractapi"
)
// SmartContract provides functions for managing an Asset
type SmartContract struct {
contractapi.Contract
}
// Asset describes basic details of what makes up a simple asset
type Asset struct {
ID string `json:"ID"`
Owner string `json:"owner"`
Value int `json:"value"`
}
// InitLedger adds a base set of assets to the ledger
func (s *SmartContract) InitLedger(ctx contractapi.TransactionContextInterface) error {
assets := []Asset{
{ID: "asset1", Owner: "Alice", Value: 100},
{ID: "asset2", Owner: "Bob", Value: 200},
}
for _, asset := range assets {
assetJSON, err := json.Marshal(asset)
if err != nil {
return err
}
err = ctx.GetStub().PutState(asset.ID, assetJSON)
if err != nil {
return fmt.Errorf("failed to put to world state. %v", err)
}
}
return nil
}
// CreateAsset issues a new asset to the world state with given details
func (s *SmartContract) CreateAsset(ctx contractapi.TransactionContextInterface, id string, owner string, value int) error {
exists, err := s.AssetExists(ctx, id)
if err != nil {
return err
}
if exists {
return fmt.Errorf("the asset %s already exists", id)
}
asset := Asset{
ID: id,
Owner: owner,
Value: value,
}
assetJSON, err := json.Marshal(asset)
if err != nil {
return err
}
return ctx.GetStub().PutState(id, assetJSON)
}
// ReadAsset returns the asset stored in the world state with given id
func (s *SmartContract) ReadAsset(ctx contractapi.TransactionContextInterface, id string) (*Asset, error) {
assetJSON, err := ctx.GetStub().GetState(id)
if err != nil {
return nil, fmt.Errorf("failed to read from world state: %v", err)
}
if assetJSON == nil {
return nil, fmt.Errorf("the asset %s does not exist", id)
}
var asset Asset
err = json.Unmarshal(assetJSON, &asset)
if err != nil {
return nil, err
}
return &asset, nil
}
// AssetExists returns true when asset with given ID exists in world state
func (s *SmartContract) AssetExists(ctx contractapi.TransactionContextInterface, id string) (bool, error) {
assetJSON, err := ctx.GetStub().GetState(id)
if err != nil {
return false, fmt.Errorf("failed to read from world state: %v", err)
}
return assetJSON != nil, nil
}
func main() {
assetChaincode, err := contractapi.NewChaincode(&SmartContract{})
if err != nil {
fmt.Printf("Error creating asset chaincode: %v", err)
return
}
if err := assetChaincode.Start(); err != nil {
fmt.Printf("Error starting asset chaincode: %v", err)
}
}
