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Generative
Programming
in Go
- GoCon 2015 summer -
@monochromegane
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MIYAKE Yusuke
(@monochromegane)
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GMO Pepabo, Inc.
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♕
3
GitHub Awards
Go ranking in Japan :)
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Generative
Programming
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ੜతͳ
Programming
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Generator
+
Template
parse generate
Parser
Your
App
Generated
Code
AST
Code
use
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Attention, please.
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✘
Generics
Meta programming
Dynamic generation
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parse
Parser
AST
Code
Go
provides
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Generator
+
Template
generate
Your
App
Generated
Code
use
We
implement
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argen
ActiveRecord Generator
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GoͰDataMapperͰͳ͘
ActiveRecordϥΠΫʹ
DBૢ࡞͢Δ
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by
Generative
programming
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ߏମʹ`+AR`ϚʔΧʔΛ͚ͭΔ
//+AR
type User struct {
Id int
Name string
Age int
}
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ੜ͢Δ
$ argen main.go
$ tree
.
!"" main.go
#"" main_gen.go
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ߏମʹARϥΠΫͳϝιου͕
Ճ͞ΕΔ
db, _ := sql.Open("sqlite3", "foo.db")
Use(db)
u := User{Name: "test", Age: 20}
u.Save()
//// INSERT INTO users (name, age) VALUES
(?, ?); [test 20]
User{}.Where("name", "test").And("age", ">",
20).Query()
//// SELECT users.id, users.name, users.age FROM
users WHERE name = ? AND age > ?; [test 20]
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Generative
Programming
͍υίϩ
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Case.1
Generics
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ҙͷߏମʹڞ௨ͷϝιου
Λ࣋ͨͤͭͭɺݸʑͷܕΛѻ͏
var u User
u = User{}.First()
var h Hoge
h = Hoge{}.First()
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ҙͷߏମʹڞ௨ͷϝιου
Λ࣋ͨͤͭͭɺݸʑͷܕΛѻ͏
var u User
u = User{}.First()
var h Hoge
h = Hoge{}.First()
• Ωϟετͨ͘͠ͳ͍
• Genericsͷग़൪
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ᵆᴸᴸᴸᴸᴸᴸᴸᴸᴸᴸᴸᴸᴸᵪᴸᴸᵊ
ᴺwhy no generics golangɹ ᴺݕࡧᴺ
ᵎᴸᴸᴸᴸᴸᴸᴸᴸᴸᴸᴸᴸᴸᵲᴸᴸᵒ
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Let’s generate !
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ߏମʹରͯ͠ݸʑͷܕΛѻ͏
ڞ௨ͷϝιουΛੜ
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func (m User) First() (*User, error) {
return m.newRelation().First()
}
func (r *UserRelation) First() (*User, error) {
return r.Order("id", "ASC").Limit(1).QueryRow()
}
func (r *UserRelation) QueryRow() (*User, error) {
row := &User{}
err := r.Relation.QueryRow(
row.fieldPtrsByName(
r.Relation.GetColumns())...)
if err != nil {
return nil, err
}
return row, nil
}
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see also: clipperhouse/gen
// +gen slice:"All"
type Person struct {
Name string
Present bool
}
gang := PersonSlice {
{"Alice", true},
{"Bob", false},
{"Carly", true},
}
here := func(p Person) bool {
return p.Present
}
gang.All(here) // => false, Bob didn't make it
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Case.2
Performance
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ϦϑϨΫγϣϯΛͬͨ൚༻ੑ
ύϑΥʔϚϯεͱҾ͖͑
// Useful! but...
var u User
db.First(&u)
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ϕϯνϚʔΫ
// read
SomeFunc(s.F)
SomeFunc(reflect.ValueOf(s).FieldByName("F").Int())
// write
s.F = 100
reflect.ValueOf(&s).Elem().FieldByName("F").SetInt(100)
$ go test -benchmem -bench .
• Mac OSX(10.10.3)
• CPU: 2.5GHz Core i5(2Core)
• Memory: 8GB
• Go: 1.4.2
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ߏମϑΟʔϧυʹର͢ΔΞΫηε
time
Alloced
Bytes
Allocs
read
field 0.38 ns 0 B 0 allocs
reflect 246 ns 16 B 2 allocs
write
field 0.36 ns 0 B 0 allocs
reflect 199 ns 8 B 1 allocs
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ෳͷߏମϑΟʔϧυʹର͢ΔΞΫηε
time
Alloced
Bytes
Allocs
read
field 0.36 ns 0 B 0 allocs
reflect 583 ns 88 B 2 allocs
write
field 0.37 ns 0 B 0 allocs
reflect 277 ns 8 B 1 allocs
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Let’s generate !
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ߏମʹରͯ͠ϑΟʔϧυใ
औಘ༻ϝιουΛੜ
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func (m *User) fieldValueByName(name string) interface{} {
switch name {
case "id", "users.id":
return m.Id
case "name", "users.name":
return m.Name
case "age", "users.age":
return m.Age
default:
return ""
}
}
func (m *User) fieldPtrByName(name string) interface{} {
switch name {
case "id", "users.id":
return &m.Id
case "name", "users.name":
return &m.Name
case "age", "users.age":
return &m.Age
default:
return nil
}
}
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see also: pquerna/ffjson
//go:generate ffjson $GOFILE
type Foo struct {
Bar string
}
f := Foo{"bar"}
b, _ := json.Marshal(f)
fmt.Printf("%s\n", string(b))
// => {"Bar":"bar"}
https://github.com/pquerna/ffjson
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Case.3
DSL
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ҙͷߏମͷڞ௨ϝιου
هड़༰͕ʹͳΓ͕ͪ
// far from the DSL...
func (u *User) BeforeUpdate() (err error) {
if u.Name != "abc"{
return fmt.Errorf("%s is invalid name.", u.Name)
}
if u.Age > 20 {
return fmt.Errorf("%d is invalid age.", u.Age)
}
return nil
}
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Let’s generate !
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ϝιου໊/ίϝϯτ/λά͔Β
ఆٛΛิͯ͠ੜ
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func (u User) validatesName() ar.Rule {
return ar.MakeRule().Format().With("abc").OnCreate()
}
func (u User) validatesAge() ar.Rule {
return ar.MakeRule().Numericality().OnlyInteger().LessThan(20)
}
rules := map[string]*ar.Validation{
"name": m.validatesName().Rule(),
"age": m.validatesAge().Rule(),
}
for name, rule := range rules {
if ok, errs :=
ar.NewValidator(rule).On(on).IsValid(m.fieldValueByName(name)); !ok {
result = false
errors.SetErrors(name, errs)
}
}
>
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Case. Bad
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ͳΜͰGenerate
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• ϝιουͷڞ௨Խɺଟଶੑͷ࣮ݱͳͲߏମͷຒࠐ
(ҕৡ)interfaceΛͬͯΔ͖
• http://go-talks.appspot.com/github.com/lestrrat/
go-slides/2014-yapcasia-go-for-perl-mongers/
main.slide#27
• http://blog.monochromegane.com/blog/
2014/03/23/struct-implementaion-patterns-in-
golang/
• Generate࣮ଆར༻ଆҰख͔͔ؒΔɺෳࡶ
ʹͳΓ͕ͪɻGenerateͰΔཧ༝͕આ໌Ͱ͖ͳ͍ͷ
Ͱ͋Ε͏͖Ͱͳ͍
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Tips
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ίϚϯυϥΠϯ/go generate
ͷ྆ํʹରԠ͢Δ
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from := os.Getenv("GOFILE")
if from == "" {
if len(args) > 0 {
from = args[0]
} else {
os.Exit(1)
}
}
$ argen main.go
// go:generate argen
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defineΛͬͯ
templateΛׂཧ͢Δ
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{{template "Relation" .}}
{{define "Relation"}}
type {{.Name}}Relation struct {
src *{{.Name}}
*ar.Relation
}
{{end}}
func (t Template) toDefine() string {
return fmt.Sprintf("{{define \"%s\"}}%s{{end}}\n",
t.Name, t.Text)
}
var relation = &Template{
Name: "Relation",
Text: `
type {{.Name}}Relation struct {
src *{{.Name}}
*ar.Relation
}`
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templateͰ
ࣗಈܗͱ
ΦʔτΠϯϙʔτ
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func writeWithFormat(file, template string, structs structs) ([]byte, error) {
var b bytes.Buffer
w := bufio.NewWriter(&b)
write(w, template, structs)
w.Flush()
formatted, err := imports.Process(file, b.Bytes(), nil)
if err != nil {
return nil, err
}
return formatted, nil
}
func write(w io.Writer, tplText string, structs structs) error {
t := template.New("t")
t.Funcs(template.FuncMap{})
tpl := template.Must(t.Parse(tplText))
if err := tpl.Execute(w, structs); err != nil {
return err
}
return nil
}
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ςετੜʹ
ରͯ͠ߦ͏
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//go:generate go run ../cmd/argen/main.go
package tests
import "github.com/monochromegane/argen"
//+AR
type User struct {
Name string
Age int
}
$ go generate && go test ./...
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એ
ϖύϘͰΤϯδχΞΛืू͍ͯ͠·͢ɻ
ڞʹαʔϏεΛੜΈग़͠ҭͯͯ͘ΕΔ৽͍ؒ͠
Λ͍ͬͯ·͢ɻ
http://pepabo.com/recruit/career/engineer/
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͓ΘΓ