Added custom error type for no book title

models/book_test.go

@@ -88,6 +88,7 @@ func TestAddOrUpdateBook(t *testing.T) {
 	// Pass an empty Book to see if it fails
 	_, err = AddOrUpdateBook(Book{})
 	assert.Error(t, err)
+	assert.True(t, IsErrBookTitleCannotBeEmpty(err))
 
 	// Update the book
 	testbook.ID = book1.ID

models/books_add_update.go

@@ -1,7 +1,5 @@
 package models
 
-import "fmt"
-
 /**
 ::USAGE::
 
@@ -21,8 +19,8 @@ sie in die Datenbank eingetragen und mit dem Buch verknüpft.
 func AddOrUpdateBook(book Book) (newBook Book, err error) {
 
 	// Check if we have at least a booktitle when we're inserting a new book
-	if book.Title == "" && book.ID == 0 {
-		return Book{}, fmt.Errorf("the book should at least have a title")
+	if book.Title == ""{
+		return Book{}, ErrBookTitleCannotBeEmpty{}
 	}
 
 	// Take Publisher, check if it exists. If not, insert it

models/error.go

@@ -91,4 +91,17 @@ func (err ErrItemTitleCannotBeEmpty) Error() string {
 	return fmt.Sprintf("title cannot be empty")
 }
 
+// ErrBookTitleCannotBeEmpty represents a "ErrBookTitleCannotBeEmpty" kind of error.
+type ErrBookTitleCannotBeEmpty struct {}
+
+// ErrBookTitleCannotBeEmpty checks if an error is a ErrBookTitleCannotBeEmpty.
+func IsErrBookTitleCannotBeEmpty(err error) bool {
+	_, ok := err.(ErrBookTitleCannotBeEmpty)
+	return ok
+}
+
+func (err ErrBookTitleCannotBeEmpty) Error() string {
+	return fmt.Sprintf("the book should at least have a title")
+}
+
 

routes/api/v1/books_add_update.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"strconv"
 	"strings"
+	"fmt"
 )
 
 // BookAddOrUpdate is the handler to add a book
@@ -62,9 +63,15 @@ func BookAddOrUpdate(c echo.Context) error {
 	newBook, err := models.AddOrUpdateBook(*datBook)
 
 	if err != nil {
+		fmt.Println(err)
 		if models.IsErrAuthorCannotBeEmpty(err) {
-			return c.JSON(http.StatusInternalServerError, models.Message{"Id cannot be 0"})
+			return c.JSON(http.StatusInternalServerError, models.Message{"Id cannot be 0."})
 		}
+
+		if models.IsErrBookTitleCannotBeEmpty(err) {
+			return c.JSON(http.StatusBadRequest, models.Message{"You need to provide at least a Title for the book."})
+		}
+
 		return c.JSON(http.StatusInternalServerError, models.Message{"Error"})
 	}