Merge pull request #223 from ybkuroki/develop

Add optional

README.md

@@ -170,10 +170,10 @@ This sample uses the following libraries.
 
 |Library Name|Version|
 |:---|:---:|
-|echo|4.7.2|
-|gorm|1.23.8|
+|echo|4.9.0|
+|gorm|1.23.10|
 |go-playground/validator.v9|9.31.0|
-|zap|1.21.0|
+|zap|1.23.0|
 
 ## Contribution
 Please read [CONTRIBUTING.md](https://github.com/ybkuroki/go-webapp-sample/blob/master/CONTRIBUTING.md) for proposing new functions, reporting bugs and submitting pull requests before contributing to this repository.

config/config.go

@@ -6,7 +6,7 @@ import (
 	"fmt"
 	"os"
 
-	"gopkg.in/yaml.v2"
+	"gopkg.in/yaml.v3"
 )
 
 // Config represents the composition of yml settings.

controller/book_test.go

@@ -36,7 +36,8 @@ func TestGetBook_Success(t *testing.T) {
 	router.ServeHTTP(rec, req)
 
 	entity := &model.Book{}
-	data, _ := entity.FindByID(container.GetRepository(), 1)
+	opt := entity.FindByID(container.GetRepository(), 1)
+	data, _ := opt.Take()
 
 	assert.Equal(t, http.StatusOK, rec.Code)
 	assert.JSONEq(t, test.ConvertToString(data), rec.Body.String())
@@ -57,7 +58,7 @@ func TestGetBook_Failure(t *testing.T) {
 	router.ServeHTTP(rec, req)
 
 	assert.Equal(t, http.StatusBadRequest, rec.Code)
-	assert.Equal(t, "\"failed to fetch data\"\n", rec.Body.String())
+	assert.Equal(t, "\"none value taken\"\n", rec.Body.String())
 }
 
 func TestGetBookList_Success(t *testing.T) {
@@ -94,7 +95,8 @@ func TestCreateBook_Success(t *testing.T) {
 	router.ServeHTTP(rec, req)
 
 	entity := &model.Book{}
-	data, _ := entity.FindByID(container.GetRepository(), 1)
+	opt := entity.FindByID(container.GetRepository(), 1)
+	data, _ := opt.Take()
 
 	assert.Equal(t, http.StatusOK, rec.Code)
 	assert.JSONEq(t, test.ConvertToString(data), rec.Body.String())
@@ -150,7 +152,8 @@ func TestUpdateBook_Success(t *testing.T) {
 	router.ServeHTTP(rec, req)
 
 	entity := &model.Book{}
-	data, _ := entity.FindByID(container.GetRepository(), 1)
+	opt := entity.FindByID(container.GetRepository(), 1)
+	data, _ := opt.Take()
 
 	assert.Equal(t, http.StatusOK, rec.Code)
 	assert.JSONEq(t, test.ConvertToString(data), rec.Body.String())
@@ -205,7 +208,8 @@ func TestDeleteBook_Success(t *testing.T) {
 	setUpTestData(container)
 
 	entity := &model.Book{}
-	data, _ := entity.FindByID(container.GetRepository(), 1)
+	opt := entity.FindByID(container.GetRepository(), 1)
+	data, _ := opt.Take()
 
 	uri := util.NewRequestBuilder().URL(APIBooks).PathParams("1").Build().GetRequestURL()
 	req := test.NewJSONRequest("DELETE", uri, nil)
@@ -279,8 +283,8 @@ func createResultForBindError() *dto.BookDto {
 
 func createResultForValidationError() map[string]string {
 	return map[string]string{
-		"isbn":  "ISBNは、10文字以上20文字以下で入力してください",
-		"title": "書籍タイトルは、3文字以上50文字以下で入力してください",
+		"isbn":  dto.ValidationErrMessageBookISBN,
+		"title": dto.ValidationErrMessageBookTitle,
 	}
 }
 

go.mod

@@ -9,16 +9,17 @@ require (
 	github.com/go-openapi/swag v0.19.15 // indirect
 	github.com/go-playground/universal-translator v0.17.0 // indirect
 	github.com/gorilla/sessions v1.2.1
-	github.com/jackc/pgproto3/v2 v2.3.0 // indirect
+	github.com/jackc/pgproto3/v2 v2.3.1 // indirect
 	github.com/labstack/echo-contrib v0.13.0
 	github.com/labstack/echo/v4 v4.9.0
 	github.com/leodido/go-urn v1.2.0 // indirect
 	github.com/mailru/easyjson v0.7.7 // indirect
 	github.com/mattn/go-isatty v0.0.14 // indirect
 	github.com/mattn/go-sqlite3 v2.0.3+incompatible // indirect
+	github.com/moznion/go-optional v0.5.0
 	github.com/stretchr/testify v1.8.0
 	github.com/swaggo/echo-swagger v1.3.4
-	github.com/swaggo/swag v1.8.5
+	github.com/swaggo/swag v1.8.6
 	github.com/valyala/fasttemplate v1.2.1
 	go.uber.org/zap v1.23.0
 	golang.org/x/crypto v0.0.0-20220722155217-630584e8d5aa
@@ -29,11 +30,11 @@ require (
 	gopkg.in/go-playground/assert.v1 v1.2.1 // indirect
 	gopkg.in/go-playground/validator.v9 v9.31.0
 	gopkg.in/natefinch/lumberjack.v2 v2.0.0
-	gopkg.in/yaml.v2 v2.4.0
+	gopkg.in/yaml.v3 v3.0.1
 	gorm.io/driver/mysql v1.3.6
-	gorm.io/driver/postgres v1.3.9
+	gorm.io/driver/postgres v1.3.10
 	gorm.io/driver/sqlite v1.3.6
-	gorm.io/gorm v1.23.8
+	gorm.io/gorm v1.23.10
 )
 
 require (
@@ -49,12 +50,12 @@ require (
 	github.com/gorilla/context v1.1.1 // indirect
 	github.com/gorilla/securecookie v1.1.1 // indirect
 	github.com/jackc/chunkreader/v2 v2.0.1 // indirect
-	github.com/jackc/pgconn v1.12.1 // indirect
+	github.com/jackc/pgconn v1.13.0 // indirect
 	github.com/jackc/pgio v1.0.0 // indirect
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20200714003250-2b9c44734f2b // indirect
-	github.com/jackc/pgtype v1.11.0 // indirect
-	github.com/jackc/pgx/v4 v4.16.1 // indirect
+	github.com/jackc/pgtype v1.12.0 // indirect
+	github.com/jackc/pgx/v4 v4.17.2 // indirect
 	github.com/jinzhu/inflection v1.0.0 // indirect
 	github.com/jinzhu/now v1.1.5 // indirect
 	github.com/josharian/intern v1.0.0 // indirect
@@ -67,5 +68,5 @@ require (
 	go.uber.org/multierr v1.6.0 // indirect
 	golang.org/x/text v0.3.7 // indirect
 	golang.org/x/time v0.0.0-20220722155302-e5dcc9cfc0b9 // indirect
-	gopkg.in/yaml.v3 v3.0.1 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
 )

go.sum

@@ -66,8 +66,8 @@ github.com/jackc/pgconn v0.0.0-20190831204454-2fabfa3c18b7/go.mod h1:ZJKsE/KZfsU
 github.com/jackc/pgconn v1.8.0/go.mod h1:1C2Pb36bGIP9QHGBYCjnyhqu7Rv3sGshaQUvmfGIB/o=
 github.com/jackc/pgconn v1.9.0/go.mod h1:YctiPyvzfU11JFxoXokUOOKQXQmDMoJL9vJzHH8/2JY=
 github.com/jackc/pgconn v1.9.1-0.20210724152538-d89c8390a530/go.mod h1:4z2w8XhRbP1hYxkpTuBjTS3ne3J48K83+u0zoyvg2pI=
-github.com/jackc/pgconn v1.12.1 h1:rsDFzIpRk7xT4B8FufgpCCeyjdNpKyghZeSefViE5W8=
-github.com/jackc/pgconn v1.12.1/go.mod h1:ZkhRC59Llhrq3oSfrikvwQ5NaxYExr6twkdkMLaKono=
+github.com/jackc/pgconn v1.13.0 h1:3L1XMNV2Zvca/8BYhzcRFS70Lr0WlDg16Di6SFGAbys=
+github.com/jackc/pgconn v1.13.0/go.mod h1:AnowpAqO4CMIIJNZl2VJp+KrkAZciAkhEl0W0JIobpI=
 github.com/jackc/pgio v1.0.0 h1:g12B9UwVnzGhueNavwioyEEpAmqMe1E/BN9ES+8ovkE=
 github.com/jackc/pgio v1.0.0/go.mod h1:oP+2QK2wFfUWgr+gxjoBH9KGBb31Eio69xUb0w5bYf8=
 github.com/jackc/pgmock v0.0.0-20190831213851-13a1b77aafa2/go.mod h1:fGZlG77KXmcq05nJLRkk0+p82V8B8Dw8KN2/V9c/OAE=
@@ -83,26 +83,26 @@ github.com/jackc/pgproto3/v2 v2.0.0-rc3/go.mod h1:ryONWYqW6dqSg1Lw6vXNMXoBJhpzvW
 github.com/jackc/pgproto3/v2 v2.0.0-rc3.0.20190831210041-4c03ce451f29/go.mod h1:ryONWYqW6dqSg1Lw6vXNMXoBJhpzvWKnT95C46ckYeM=
 github.com/jackc/pgproto3/v2 v2.0.6/go.mod h1:WfJCnwN3HIg9Ish/j3sgWXnAfK8A9Y0bwXYU5xKaEdA=
 github.com/jackc/pgproto3/v2 v2.1.1/go.mod h1:WfJCnwN3HIg9Ish/j3sgWXnAfK8A9Y0bwXYU5xKaEdA=
-github.com/jackc/pgproto3/v2 v2.3.0 h1:brH0pCGBDkBW07HWlN/oSBXrmo3WB0UvZd1pIuDcL8Y=
-github.com/jackc/pgproto3/v2 v2.3.0/go.mod h1:WfJCnwN3HIg9Ish/j3sgWXnAfK8A9Y0bwXYU5xKaEdA=
+github.com/jackc/pgproto3/v2 v2.3.1 h1:nwj7qwf0S+Q7ISFfBndqeLwSwxs+4DPsbRFjECT1Y4Y=
+github.com/jackc/pgproto3/v2 v2.3.1/go.mod h1:WfJCnwN3HIg9Ish/j3sgWXnAfK8A9Y0bwXYU5xKaEdA=
 github.com/jackc/pgservicefile v0.0.0-20200714003250-2b9c44734f2b h1:C8S2+VttkHFdOOCXJe+YGfa4vHYwlt4Zx+IVXQ97jYg=
 github.com/jackc/pgservicefile v0.0.0-20200714003250-2b9c44734f2b/go.mod h1:vsD4gTJCa9TptPL8sPkXrLZ+hDuNrZCnj29CQpr4X1E=
 github.com/jackc/pgtype v0.0.0-20190421001408-4ed0de4755e0/go.mod h1:hdSHsc1V01CGwFsrv11mJRHWJ6aifDLfdV3aVjFF0zg=
 github.com/jackc/pgtype v0.0.0-20190824184912-ab885b375b90/go.mod h1:KcahbBH1nCMSo2DXpzsoWOAfFkdEtEJpPbVLq8eE+mc=
 github.com/jackc/pgtype v0.0.0-20190828014616-a8802b16cc59/go.mod h1:MWlu30kVJrUS8lot6TQqcg7mtthZ9T0EoIBFiJcmcyw=
 github.com/jackc/pgtype v1.8.1-0.20210724151600-32e20a603178/go.mod h1:C516IlIV9NKqfsMCXTdChteoXmwgUceqaLfjg2e3NlM=
-github.com/jackc/pgtype v1.11.0 h1:u4uiGPz/1hryuXzyaBhSk6dnIyyG2683olG2OV+UUgs=
-github.com/jackc/pgtype v1.11.0/go.mod h1:LUMuVrfsFfdKGLw+AFFVv6KtHOFMwRgDDzBt76IqCA4=
+github.com/jackc/pgtype v1.12.0 h1:Dlq8Qvcch7kiehm8wPGIW0W3KsCCHJnRacKW0UM8n5w=
+github.com/jackc/pgtype v1.12.0/go.mod h1:LUMuVrfsFfdKGLw+AFFVv6KtHOFMwRgDDzBt76IqCA4=
 github.com/jackc/pgx/v4 v4.0.0-20190420224344-cc3461e65d96/go.mod h1:mdxmSJJuR08CZQyj1PVQBHy9XOp5p8/SHH6a0psbY9Y=
 github.com/jackc/pgx/v4 v4.0.0-20190421002000-1b8f0016e912/go.mod h1:no/Y67Jkk/9WuGR0JG/JseM9irFbnEPbuWV2EELPNuM=
 github.com/jackc/pgx/v4 v4.0.0-pre1.0.20190824185557-6972a5742186/go.mod h1:X+GQnOEnf1dqHGpw7JmHqHc1NxDoalibchSk9/RWuDc=
 github.com/jackc/pgx/v4 v4.12.1-0.20210724153913-640aa07df17c/go.mod h1:1QD0+tgSXP7iUjYm9C1NxKhny7lq6ee99u/z+IHFcgs=
-github.com/jackc/pgx/v4 v4.16.1 h1:JzTglcal01DrghUqt+PmzWsZx/Yh7SC/CTQmSBMTd0Y=
-github.com/jackc/pgx/v4 v4.16.1/go.mod h1:SIhx0D5hoADaiXZVyv+3gSm3LCIIINTVO0PficsvWGQ=
+github.com/jackc/pgx/v4 v4.17.2 h1:0Ut0rpeKwvIVbMQ1KbMBU4h6wxehBI535LK6Flheh8E=
+github.com/jackc/pgx/v4 v4.17.2/go.mod h1:lcxIZN44yMIrWI78a5CpucdD14hX0SBDbNRvjDBItsw=
 github.com/jackc/puddle v0.0.0-20190413234325-e4ced69a3a2b/go.mod h1:m4B5Dj62Y0fbyuIc15OsIqK0+JU8nkqQjsgx7dvjSWk=
 github.com/jackc/puddle v0.0.0-20190608224051-11cab39313c9/go.mod h1:m4B5Dj62Y0fbyuIc15OsIqK0+JU8nkqQjsgx7dvjSWk=
 github.com/jackc/puddle v1.1.3/go.mod h1:m4B5Dj62Y0fbyuIc15OsIqK0+JU8nkqQjsgx7dvjSWk=
-github.com/jackc/puddle v1.2.1/go.mod h1:m4B5Dj62Y0fbyuIc15OsIqK0+JU8nkqQjsgx7dvjSWk=
+github.com/jackc/puddle v1.3.0/go.mod h1:m4B5Dj62Y0fbyuIc15OsIqK0+JU8nkqQjsgx7dvjSWk=
 github.com/jinzhu/inflection v1.0.0 h1:K317FqzuhWc8YvSVlFMCCUb36O/S9MCKRDI7QkRKD/E=
 github.com/jinzhu/inflection v1.0.0/go.mod h1:h+uFLlag+Qp1Va5pdKtLDYj+kHp5pxUVkryuEj+Srlc=
 github.com/jinzhu/now v1.1.4/go.mod h1:d3SSVoowX0Lcu0IBviAWJpolVfI5UJVZZ7cO71lE/z8=
@@ -152,6 +152,8 @@ github.com/mattn/go-isatty v0.0.14/go.mod h1:7GGIvUiUoEMVVmxf/4nioHXj79iQHKdU27k
 github.com/mattn/go-sqlite3 v1.14.12/go.mod h1:NyWgC/yNuGj7Q9rpYnZvas74GogHl5/Z4A/KQRfk6bU=
 github.com/mattn/go-sqlite3 v2.0.3+incompatible h1:gXHsfypPkaMZrKbD5209QV9jbUTJKjyR5WD3HYQSd+U=
 github.com/mattn/go-sqlite3 v2.0.3+incompatible/go.mod h1:FPy6KqzDD04eiIsT53CuJW3U88zkxoIYsOqkbpncsNc=
+github.com/moznion/go-optional v0.5.0 h1:BGfkHyvSbdfGP4F7x7ywxg6wltAagG/BGOXoEyBTBlQ=
+github.com/moznion/go-optional v0.5.0/go.mod h1:lTyBRKsQPhzFQZb5M+v4cCOYLuD9JUgP0izTOjR8lsw=
 github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e h1:fD57ERR4JtEqsWbfPhv4DMiApHyliiK5xCTNVSPiaAs=
 github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e/go.mod h1:zD1mROLANZcx1PVRCS0qkT7pwLkGfwJo4zjcN/Tysno=
 github.com/otiai10/copy v1.7.0/go.mod h1:rmRl6QPdJj6EiUqXQ/4Nn2lLXoNQjFCQbbNrxgc/t3U=
@@ -195,8 +197,8 @@ github.com/swaggo/echo-swagger v1.3.4/go.mod h1:vh8QAdbHtTXwTSaWzc1Nby7zMYJd/g0F
 github.com/swaggo/files v0.0.0-20220728132757-551d4a08d97a h1:kAe4YSu0O0UFn1DowNo2MY5p6xzqtJ/wQ7LZynSvGaY=
 github.com/swaggo/files v0.0.0-20220728132757-551d4a08d97a/go.mod h1:lKJPbtWzJ9JhsTN1k1gZgleJWY/cqq0psdoMmaThG3w=
 github.com/swaggo/swag v1.8.1/go.mod h1:ugemnJsPZm/kRwFUnzBlbHRd0JY9zE1M4F+uy2pAaPQ=
-github.com/swaggo/swag v1.8.5 h1:7NgtfXsXE+jrcOwRyiftGKW7Ppydj7tZiVenuRf1fE4=
-github.com/swaggo/swag v1.8.5/go.mod h1:jMLeXOOmYyjk8PvHTsXBdrubsNd9gUJTTCzL5iBnseg=
+github.com/swaggo/swag v1.8.6 h1:2rgOaLbonWu1PLP6G+/rYjSvPg0jQE0HtrEKuE380eg=
+github.com/swaggo/swag v1.8.6/go.mod h1:jMLeXOOmYyjk8PvHTsXBdrubsNd9gUJTTCzL5iBnseg=
 github.com/urfave/cli/v2 v2.3.0/go.mod h1:LJmUH05zAU44vOAcrfzZQKsZbVcdbOG8rtL3/XcUArI=
 github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6KllzawFIhcdPw=
 github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
@@ -338,12 +340,13 @@ gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gorm.io/driver/mysql v1.3.6 h1:BhX1Y/RyALb+T9bZ3t07wLnPZBukt+IRkMn8UZSNbGM=
 gorm.io/driver/mysql v1.3.6/go.mod h1:sSIebwZAVPiT+27jK9HIwvsqOGKx3YMPmrA3mBJR10c=
-gorm.io/driver/postgres v1.3.9 h1:lWGiVt5CijhQAg0PWB7Od1RNcBw/jS4d2cAScBcSDXg=
-gorm.io/driver/postgres v1.3.9/go.mod h1:qw/FeqjxmYqW5dBcYNBsnhQULIApQdk7YuuDPktVi1U=
+gorm.io/driver/postgres v1.3.10 h1:Fsd+pQpFMGlGxxVMUPJhNo8gG8B1lKtk8QQ4/VZZAJw=
+gorm.io/driver/postgres v1.3.10/go.mod h1:whNfh5WhhHs96honoLjBAMwJGYEuA3m1hvgUbNXhPCw=
 gorm.io/driver/sqlite v1.3.6 h1:Fi8xNYCUplOqWiPa3/GuCeowRNBRGTf62DEmhMDHeQQ=
 gorm.io/driver/sqlite v1.3.6/go.mod h1:Sg1/pvnKtbQ7jLXxfZa+jSHvoX8hoZA8cn4xllOMTgE=
 gorm.io/gorm v1.23.4/go.mod h1:l2lP/RyAtc1ynaTjFksBde/O8v9oOGIApu2/xRitmZk=
 gorm.io/gorm v1.23.7/go.mod h1:l2lP/RyAtc1ynaTjFksBde/O8v9oOGIApu2/xRitmZk=
-gorm.io/gorm v1.23.8 h1:h8sGJ+biDgBA1AD1Ha9gFCx7h8npU7AsLdlkX0n2TpE=
 gorm.io/gorm v1.23.8/go.mod h1:l2lP/RyAtc1ynaTjFksBde/O8v9oOGIApu2/xRitmZk=
+gorm.io/gorm v1.23.10 h1:4Ne9ZbzID9GUxRkllxN4WjJKpsHx8YbKvekVdgyWh24=
+gorm.io/gorm v1.23.10/go.mod h1:DVrVomtaYTbqs7gB/x2uVvqnXzv0nqjB396B8cG4dBA=
 honnef.co/go/tools v0.0.1-2019.2.3/go.mod h1:a3bituU0lyd329TUQxRnasdCoJDkEUEAqEt0JzvZhAg=

logger/logger.go

@@ -9,7 +9,7 @@ import (
 
 	"go.uber.org/zap"
 	"gopkg.in/natefinch/lumberjack.v2"
-	"gopkg.in/yaml.v2"
+	"gopkg.in/yaml.v3"
 	gormLogger "gorm.io/gorm/logger"
 )
 

model/account.go

@@ -1,8 +1,6 @@
 package model
 
 import (
-	"encoding/json"
-
 	"github.com/ybkuroki/go-webapp-sample/repository"
 	"golang.org/x/crypto/bcrypt"
 )
@@ -70,7 +68,6 @@ func convertToAccount(rec *RecordAccount) *Account {
 }
 
 // ToString is return string of object
-func (a *Account) ToString() (string, error) {
-	bytes, err := json.Marshal(a)
-	return string(bytes), err
+func (a *Account) ToString() string {
+	return toString(a)
 }

model/authority.go

@@ -1,8 +1,6 @@
 package model
 
 import (
-	"encoding/json"
-
 	"github.com/ybkuroki/go-webapp-sample/repository"
 )
 
@@ -31,7 +29,6 @@ func (a *Authority) Create(rep repository.Repository) (*Authority, error) {
 }
 
 // ToString is return string of object
-func (a *Authority) ToString() (string, error) {
-	bytes, err := json.Marshal(a)
-	return string(bytes), err
+func (a *Authority) ToString() string {
+	return toString(a)
 }

model/base.go

@@ -0,0 +1,18 @@
+package model
+
+import "encoding/json"
+
+// DomainObject defines the common interface for domain models.
+type DomainObject interface {
+	Account | Authority | Book | Category | Format
+}
+
+// toString returns the JSON data of the domain models.
+func toString[T DomainObject](o *T) string {
+	var bytes []byte
+	var err error
+	if bytes, err = json.Marshal(o); err != nil {
+		return ""
+	}
+	return string(bytes)
+}

model/book.go

@@ -2,10 +2,10 @@ package model
 
 import (
 	"database/sql"
-	"encoding/json"
 	"errors"
 	"math"
 
+	"github.com/moznion/go-optional"
 	"github.com/ybkuroki/go-webapp-sample/repository"
 	"github.com/ybkuroki/go-webapp-sample/util"
 	"gorm.io/gorm"
@@ -52,7 +52,7 @@ func NewBook(title string, isbn string, categoryID uint, formatID uint) *Book {
 }
 
 // FindByID returns a book full matched given book's ID.
-func (b *Book) FindByID(rep repository.Repository, id uint) (*Book, error) {
+func (b *Book) FindByID(rep repository.Repository, id uint) optional.Option[*Book] {
 	var rec RecordBook
 	args := []interface{}{id}
 
@@ -110,10 +110,12 @@ func findRows(rep repository.Repository, sqlquery string, page string, size stri
 		if err = rep.ScanRows(rows, &rec); err != nil {
 			return nil, err
 		}
-		book, err := convertToBook(&rec)
-		if err != nil {
-			return nil, err
+
+		opt := convertToBook(&rec)
+		if opt.IsNone() {
+			return nil, errors.New("failed to fetch data")
 		}
+		book, _ := opt.Take()
 		books = append(books, *book)
 	}
 	return books, nil
@@ -179,17 +181,17 @@ func (b *Book) Delete(rep repository.Repository) (*Book, error) {
 	return b, nil
 }
 
-func convertToBook(rec *RecordBook) (*Book, error) {
+func convertToBook(rec *RecordBook) optional.Option[*Book] {
 	if rec.ID == 0 {
-		return nil, errors.New("failed to fetch data")
+		return optional.None[*Book]()
 	}
 	c := &Category{ID: rec.CategoryID, Name: rec.CategoryName}
 	f := &Format{ID: rec.FormatID, Name: rec.FormatName}
-	return &Book{ID: rec.ID, Title: rec.Title, Isbn: rec.Isbn, CategoryID: rec.CategoryID, Category: c, FormatID: rec.FormatID, Format: f}, nil
+	return optional.Some(
+		&Book{ID: rec.ID, Title: rec.Title, Isbn: rec.Isbn, CategoryID: rec.CategoryID, Category: c, FormatID: rec.FormatID, Format: f})
 }
 
 // ToString is return string of object
-func (b *Book) ToString() (string, error) {
-	bytes, err := json.Marshal(b)
-	return string(bytes), err
+func (b *Book) ToString() string {
+	return toString(b)
 }

model/category.go

@@ -1,8 +1,7 @@
 package model
 
 import (
-	"encoding/json"
-
+	"github.com/moznion/go-optional"
 	"github.com/ybkuroki/go-webapp-sample/repository"
 )
 
@@ -35,12 +34,12 @@ func (c *Category) Exist(rep repository.Repository, id uint) (bool, error) {
 }
 
 // FindByID returns a category full matched given category's ID.
-func (c *Category) FindByID(rep repository.Repository, id uint) (*Category, error) {
+func (c *Category) FindByID(rep repository.Repository, id uint) optional.Option[*Category] {
 	var category Category
 	if err := rep.Where("id = ?", id).First(&category).Error; err != nil {
-		return nil, err
+		return optional.None[*Category]()
 	}
-	return &category, nil
+	return optional.Some(&category)
 }
 
 // FindAll returns all categories of the category table.
@@ -61,7 +60,6 @@ func (c *Category) Create(rep repository.Repository) (*Category, error) {
 }
 
 // ToString is return string of object
-func (c *Category) ToString() (string, error) {
-	bytes, err := json.Marshal(c)
-	return string(bytes), err
+func (c *Category) ToString() string {
+	return toString(c)
 }