Hyperledger fabric2.4 鍊碼編寫

fabric提供了fabric-contract-api-go和fabric-chaincode-go兩個包來編寫鍊碼， 這裡以fabric-contract-api-go為例進行鍊碼編寫

1、聲明合約

package main

import (
    "errors"
    "fmt"

    "github.com/hyperledger/fabric-contract-api-go/contractapi"
)
type SimpleContract struct {
    contractapi.Contract
}
           

2、編寫合約函數

規則：

1、第一個參數必須是*contractapi.TransactionContext類型

2、函數最多傳回兩個值，第二個值必須是error類型

// 添加資料
func (sc *SimpleContract) Create(ctx contractapi.TransactionContextInterface, key string, value string) error {
    existing, err := ctx.GetStub().GetState(key)

    if err != nil {
        return errors.New("Unable to interact with world state")
    }

    if existing != nil {
        return fmt.Errorf("Cannot create world state pair with key %s. Already exists", key)
    }
	
    err = ctx.GetStub().PutState(key, []byte(value))

    if err != nil {
        return errors.New("Unable to interact with world state")
    }

    return nil
}

// 讀取資料
func (sc *SimpleContract) Read(ctx contractapi.TransactionContextInterface, key string) (string, error) {
    existing, err := ctx.GetStub().GetState(key)

    if err != nil {
        return "", errors.New("Unable to interact with world state")
    }

    if existing == nil {
        return "", fmt.Errorf("Cannot read world state pair with key %s. Does not exist", key)
    }

    return string(existing), nil
}
           

3、建立并啟動鍊碼

package main

import (
    "github.com/hyperledger/fabric-contract-api-go/contractapi"
)

func main() {
    simpleContract := new(SimpleContract)

    cc, err := contractapi.NewChaincode(simpleContract)

    if err != nil {
        panic(err.Error())
    }

    if err := cc.Start(); err != nil {
        panic(err.Error())
    }
}
           

完整合約代碼：

package main

import (
    "errors"
    "fmt"

    "github.com/hyperledger/fabric-contract-api-go/contractapi"
)

type SimpleContract struct {
    contractapi.Contract
}

// 添加資料
func (sc *SimpleContract) Create(ctx contractapi.TransactionContextInterface, key string, value string) error {
    existing, err := ctx.GetStub().GetState(key)

    if err != nil {
        return errors.New("Unable to interact with world state")
    }

    if existing != nil {
        return fmt.Errorf("Cannot create world state pair with key %s. Already exists", key)
    }
	
    err = ctx.GetStub().PutState(key, []byte(value))

    if err != nil {
        return errors.New("Unable to interact with world state")
    }

    return nil
}

// 讀取資料
func (sc *SimpleContract) Read(ctx contractapi.TransactionContextInterface, key string) (string, error) {
    existing, err := ctx.GetStub().GetState(key)

    if err != nil {
        return "", errors.New("Unable to interact with world state")
    }

    if existing == nil {
        return "", fmt.Errorf("Cannot read world state pair with key %s. Does not exist", key)
    }

    return string(existing), nil
}

func main() {
    simpleContract := new(SimpleContract)

    cc, err := contractapi.NewChaincode(simpleContract)

    if err != nil {
        panic(err.Error())
    }

    if err := cc.Start(); err != nil {
        panic(err.Error())
    }
}

           

一個簡單的智能合約就編寫完了