Format Fabcar Chaincode in Idiomatic Go

Signed-off-by: Brett Logan <brett.t.logan@ibm.com>

chaincode/fabcar/go/fabcar.go

@@ -7,7 +7,7 @@ package main
 import (
 	"encoding/json"
 	"fmt"
-	"strconv"
+	"log"
 
 	"github.com/hyperledger/fabric-contract-api-go/contractapi"
 )
@@ -34,24 +34,24 @@ type QueryResult struct {
 // InitLedger adds a base set of cars to the ledger
 func (s *SmartContract) InitLedger(ctx contractapi.TransactionContextInterface) error {
 	cars := []Car{
-		Car{Make: "Toyota", Model: "Prius", Colour: "blue", Owner: "Tomoko"},
+		{Make: "Toyota", Model: "Prius", Colour: "blue", Owner: "Tomoko"},
-		Car{Make: "Ford", Model: "Mustang", Colour: "red", Owner: "Brad"},
+		{Make: "Ford", Model: "Mustang", Colour: "red", Owner: "Brad"},
-		Car{Make: "Hyundai", Model: "Tucson", Colour: "green", Owner: "Jin Soo"},
+		{Make: "Hyundai", Model: "Tucson", Colour: "green", Owner: "Jin Soo"},
-		Car{Make: "Volkswagen", Model: "Passat", Colour: "yellow", Owner: "Max"},
+		{Make: "Volkswagen", Model: "Passat", Colour: "yellow", Owner: "Max"},
-		Car{Make: "Tesla", Model: "S", Colour: "black", Owner: "Adriana"},
+		{Make: "Tesla", Model: "S", Colour: "black", Owner: "Adriana"},
-		Car{Make: "Peugeot", Model: "205", Colour: "purple", Owner: "Michel"},
+		{Make: "Peugeot", Model: "205", Colour: "purple", Owner: "Michel"},
-		Car{Make: "Chery", Model: "S22L", Colour: "white", Owner: "Aarav"},
+		{Make: "Chery", Model: "S22L", Colour: "white", Owner: "Aarav"},
-		Car{Make: "Fiat", Model: "Punto", Colour: "violet", Owner: "Pari"},
+		{Make: "Fiat", Model: "Punto", Colour: "violet", Owner: "Pari"},
-		Car{Make: "Tata", Model: "Nano", Colour: "indigo", Owner: "Valeria"},
+		{Make: "Tata", Model: "Nano", Colour: "indigo", Owner: "Valeria"},
-		Car{Make: "Holden", Model: "Barina", Colour: "brown", Owner: "Shotaro"},
+		{Make: "Holden", Model: "Barina", Colour: "brown", Owner: "Shotaro"},
 	}
 
 	for i, car := range cars {
 		carAsBytes, _ := json.Marshal(car)
-		err := ctx.GetStub().PutState("CAR"+strconv.Itoa(i), carAsBytes)
+		key := fmt.Sprintf("CAR%d", i)
-
+		err := ctx.GetStub().PutState(key, carAsBytes)
 		if err != nil {
-			return fmt.Errorf("Failed to put to world state. %s", err.Error())
+			return fmt.Errorf("failed to put to world state. %v", err)
 		}
 	}
 
@@ -66,86 +66,79 @@ func (s *SmartContract) CreateCar(ctx contractapi.TransactionContextInterface, c
 		Colour: colour,
 		Owner:  owner,
 	}
-
+	carAsBytes, err := json.Marshal(car)
-	carAsBytes, _ := json.Marshal(car)
+	if err != nil {
-
+		return fmt.Errorf("failed marshalling to json: %v", err)
+	}
 	return ctx.GetStub().PutState(carNumber, carAsBytes)
 }
 
 // QueryCar returns the car stored in the world state with given id
 func (s *SmartContract) QueryCar(ctx contractapi.TransactionContextInterface, carNumber string) (*Car, error) {
 	carAsBytes, err := ctx.GetStub().GetState(carNumber)
-
 	if err != nil {
-		return nil, fmt.Errorf("Failed to read from world state. %s", err.Error())
+		return nil, fmt.Errorf("failed to read from world state: %v", err)
 	}
-
 	if carAsBytes == nil {
 		return nil, fmt.Errorf("%s does not exist", carNumber)
 	}
-
+	var car *Car
-	car := new(Car)
+	err = json.Unmarshal(carAsBytes, car)
-	_ = json.Unmarshal(carAsBytes, car)
+	if err != nil {
-
+		return nil, err
+	}
 	return car, nil
 }
 
 // QueryAllCars returns all cars found in world state
 func (s *SmartContract) QueryAllCars(ctx contractapi.TransactionContextInterface) ([]QueryResult, error) {
-	startKey := ""
+	// Return all cars by using empty startKey and endKey
-	endKey := ""
+	resultsIterator, err := ctx.GetStub().GetStateByRange("", "")
-
-	resultsIterator, err := ctx.GetStub().GetStateByRange(startKey, endKey)
-
 	if err != nil {
 		return nil, err
 	}
 	defer resultsIterator.Close()
 
-	results := []QueryResult{}
+	var results []QueryResult
-
 	for resultsIterator.HasNext() {
 		queryResponse, err := resultsIterator.Next()
-
 		if err != nil {
 			return nil, err
 		}
 
-		car := new(Car)
+		var car *Car
-		_ = json.Unmarshal(queryResponse.Value, car)
+		err = json.Unmarshal(queryResponse.Value, car)
-
+		if err != nil {
+			return nil, fmt.Errorf("failed marshalling to json: %v", err)
+		}
 		queryResult := QueryResult{Key: queryResponse.Key, Record: car}
 		results = append(results, queryResult)
 	}
-
 	return results, nil
 }
 
 // ChangeCarOwner updates the owner field of car with given id in world state
 func (s *SmartContract) ChangeCarOwner(ctx contractapi.TransactionContextInterface, carNumber string, newOwner string) error {
 	car, err := s.QueryCar(ctx, carNumber)
-
 	if err != nil {
 		return err
 	}
 
 	car.Owner = newOwner
-
+	carAsBytes, err := json.Marshal(car)
-	carAsBytes, _ := json.Marshal(car)
+	if err != nil {
-
+		return fmt.Errorf("failed marshalling to json: %v", err)
+	}
 	return ctx.GetStub().PutState(carNumber, carAsBytes)
 }
 
 func main() {
-
+	chaincode, err := contractapi.NewChaincode(&SmartContract{})
-	chaincode, err := contractapi.NewChaincode(new(SmartContract))
-
 	if err != nil {
-		fmt.Printf("Error create fabcar chaincode: %s", err.Error())
+		log.Panicf("Error create fabcar chaincode: %v", err)
-		return
 	}
 
 	if err := chaincode.Start(); err != nil {
-		fmt.Printf("Error starting fabcar chaincode: %s", err.Error())
+		log.Panicf("Error starting fabcar chaincode: %v", err)
 	}
 }