寫入區塊聯繫

		
func (s *SmartContract) initLedger(stub shim.ChaincodeStubInterface) sc.Response {
	
	token := &Token{
		Owner: "netkiller",
		TotalSupply: 10000,
		TokenName: "代幣通正",
		TokenSymbol: "COIN",
		BalanceOf: map[string]uint{}}
	
	token.initialSupply()

	tokenAsBytes, _ := json.Marshal(token)
	stub.PutState("Token", tokenAsBytes)
	fmt.Println("Added", tokenAsBytes)
	
	return shim.Success(nil)
}		
		
			

通過key獲取區塊信息

		
func (s *SmartContract) balanceToken(stub shim.ChaincodeStubInterface, args []string) sc.Response {

	if len(args) != 1 {
		return shim.Error("Incorrect number of arguments. Expecting 1")
	}

	tokenAsBytes, _ := stub.GetState(args[0])
	token := Token{}

	json.Unmarshal(tokenAsBytes, &token)
	amount := token.balance(args[1])

	return shim.Success(amount)
}
		
			

刪除區塊信息

		
func (s *SmartContract) deleteData(stub shim.ChaincodeStubInterface, args []string) sc.Response {
	if len(args) != 1 {
		return shim.Error("Incorrect number of arguments. Expecting 1")
	}
	err= stub.DelState(args[0])
	if err != nil {
	   return shim.Error("Failed to delete Student from DB, key is: "+key)
	}
	return shim.Success(nil)
}
		
			

State 資料庫並沒有提供修改功能，修改數據可以先讀取，再修改，最後寫入

		
func (s *SmartContract) transferToken(stub shim.ChaincodeStubInterface, args []string) sc.Response {

	if len(args) != 3 {
		return shim.Error("Incorrect number of arguments. Expecting 2")
	}

	tokenAsBytes, _ := stub.GetState(args[0])
	token := Token{}

	json.Unmarshal(tokenAsBytes, &token)
	token.transfer(args[1],args[2],args[3])

	tokenAsBytes, _ = json.Marshal(token)
	stub.PutState(args[0], tokenAsBytes)

	return shim.Success(nil)
}
		
			

區塊鏈是一個線性的資料結構，只要知道開始位置，結束位置，就能夠取出中間部分的數據。

			
func (s *SmartContract) queryAllCars(APIstub shim.ChaincodeStubInterface) sc.Response {

	startKey := "CAR0"
	endKey := "CAR999"

	resultsIterator, err := APIstub.GetStateByRange(startKey, endKey)
	if err != nil {
		return shim.Error(err.Error())
	}
	defer resultsIterator.Close()

	// buffer is a JSON array containing QueryResults
	var buffer bytes.Buffer
	buffer.WriteString("[")

	bArrayMemberAlreadyWritten := false
	for resultsIterator.HasNext() {
		queryResponse, err := resultsIterator.Next()
		if err != nil {
			return shim.Error(err.Error())
		}
		// Add a comma before array members, suppress it for the first array member
		if bArrayMemberAlreadyWritten == true {
			buffer.WriteString(",")
		}
		buffer.WriteString("{\"Key\":")
		buffer.WriteString("\"")
		buffer.WriteString(queryResponse.Key)
		buffer.WriteString("\"")

		buffer.WriteString(", \"Record\":")
		// Record is a JSON object, so we write as-is
		buffer.WriteString(string(queryResponse.Value))
		buffer.WriteString("}")
		bArrayMemberAlreadyWritten = true
	}
	buffer.WriteString("]")

	fmt.Printf("- queryAllCars:\n%s\n", buffer.String())

	return shim.Success(buffer.Bytes())
}
			
			
			

GetQueryResult 能查詢 json 裡面的數據

下面例子是 Name = Neo Chen 的所有數據。

			
func (t *SimpleChaincode) getQueryResult(stub shim.ChaincodeStubInterface, args []string) pb.Response{
   name:="Neo Chen"	//需要查詢的名字
   queryString := fmt.Sprintf("{\"selector\":{\"Name\":\"%s\"}}", name)
   resultsIterator,err:= stub.GetQueryResult(queryString)//必須是CouchDB才行
   if err!=nil{
      return shim.Error("query failed")
   }
   person,err:=getListResult(resultsIterator)
   if err!=nil{
      return shim.Error("query failed")
   }
   return shim.Success(person)
}
			
			

通過key獲取歷史數據

			
func (t *SimpleChaincode) historyQuery(stub shim.ChaincodeStubInterface, args []string) pb.Response{

	if len(args) != 1 {
		return shim.Error("Incorrect number of arguments. Expecting 1")
	}
   
   it,err:= stub.GetHistoryForKey(args[0])
   if err!=nil{
      return shim.Error(err.Error())
   }
   var result,_= getHistoryListResult(it)
   return shim.Success(result)
}			
			
			

			
func getHistoryListResult(resultsIterator shim.HistoryQueryIteratorInterface) ([]byte,error){

   defer resultsIterator.Close()
   // buffer is a JSON array containing QueryRecords
   var buffer bytes.Buffer
   buffer.WriteString("[")

   bArrayMemberAlreadyWritten := false
   for resultsIterator.HasNext() {
      queryResponse, err := resultsIterator.Next()
      if err != nil {
         return nil, err
      }
      // Add a comma before array members, suppress it for the first array member
      if bArrayMemberAlreadyWritten == true {
         buffer.WriteString(",")
      }
      item,_:= json.Marshal( queryResponse)
      buffer.Write(item)
      bArrayMemberAlreadyWritten = true
   }
   buffer.WriteString("]")
   fmt.Printf("queryResult:\n%s\n", buffer.String())
   return buffer.Bytes(), nil
}	
			
			

			
	// maintain the index
	indexName := "color~name"
	colorNameIndexKey, err := stub.CreateCompositeKey(indexName, []string{marbleJSON.Color, marbleJSON.Name})
	if err != nil {
		return shim.Error(err.Error())
	}

	//  Delete index entry to state.
	err = stub.DelState(colorNameIndexKey)
	if err != nil {
		return shim.Error("Failed to delete state:" + err.Error())
	}	
			
			

			
		// get the color and name from color~name composite key
		objectType, compositeKeyParts, err := stub.SplitCompositeKey(responseRange.Key)
		if err != nil {
			return shim.Error(err.Error())
		}
		returnedColor := compositeKeyParts[0]
		returnedMarbleName := compositeKeyParts[1]