error handling in go

Author: Ady Rahmat MA

examples/10_error_handling/main.go

@@ -0,0 +1,80 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"strconv"
+)
+
+func main() {
+	// in go, there are no exceptions
+	// in go, error handled using return values
+
+	// try to use strconv package from go
+	// we are going to convert x into integer
+	x := "name"
+	n, err := strconv.Atoi(x)
+	if err != nil {
+		log.Printf("x cannot be converted to an integer. err: %s\n", err.Error())
+	} else {
+		log.Printf("n: %d is integer value of x\n", n)
+	}
+
+	// err is an interface value from "error" interface
+	// and because its an interface, we can define our own error
+
+	// using package errors to define error
+	err = check(x)
+	if err != nil {
+		log.Printf("got err: %s\n", err.Error())
+	}
+
+	// using defined variables, it is very usefull
+	// like catching exception on other language
+	err = anotherCheck(x)
+	if err == ErrInvalidLength {
+		log.Println("X is less than 5 char")
+	}
+
+	// using type struct, which we can got more information about the error
+	// we can do type assertion here
+	err = checkString(x)
+	terr, ok := err.(MyError)
+	if ok {
+		log.Println(terr.Error())
+		log.Printf("%d: %s\n", terr.Code, terr.Message)
+	}
+}
+
+func check(x string) error {
+	if len(x) < 5 {
+		return errors.New("Invalid Length")
+	}
+	return nil
+}
+
+var ErrInvalidLength = errors.New("Invalid Length")
+
+func anotherCheck(x string) error {
+	if len(x) < 5 {
+		return ErrInvalidLength
+	}
+	return nil
+}
+
+type MyError struct {
+	Code    int
+	Message string
+}
+
+func (e MyError) Error() string {
+	return fmt.Sprintf("%d: %s", e.Code, e.Message)
+}
+
+func checkString(x string) error {
+	if len(x) < 5 {
+		return MyError{Code: 409, Message: "Invalid Length"}
+	}
+	return nil
+}