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@tp /main.go
Created Oct 20, 2014

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package main
import (
"fmt"
"time"
"appengine"
"appengine/datastore"
)
const (
KindUser = "user"
KindUserProfile = "userprofile"
)
func main() {}
type CreatedAtStruct struct {
CreatedAt time.Time
}
func (c *CreatedAtStruct) SetCreatedAt(t time.Time) {
c.CreatedAt = t
}
type CreationDateSetter interface {
SetCreatedAt(t time.Time)
}
type User struct{}
type UserProfile struct {
CreatedAtStruct
Counter int
}
func putVersioned(c appengine.Context, kind string, parent *datastore.Key, v CreationDateSetter) (*datastore.Key, error) {
if parent == nil {
return nil, fmt.Errorf("parent must be set")
}
v.SetCreatedAt(time.Now())
return datastore.Put(c, datastore.NewIncompleteKey(c, kind, parent), v)
}
func getLatest(c appengine.Context, kind string, parent *datastore.Key, v interface{}) error {
q := datastore.NewQuery(kind).Ancestor(parent).Order("-CreatedAt").Limit(1)
_, err := q.Run(c).Next(v)
return err
}
package main
import (
"testing"
"appengine/aetest"
"appengine/datastore"
)
func TestVersionedStorageAfterEachPut(t *testing.T) {
c, err := aetest.NewContext(nil)
if err != nil {
t.Fatal(err)
}
userkey, err := datastore.Put(c, datastore.NewIncompleteKey(c, KindUser, nil), &User{})
if err != nil {
t.Fatal(err)
}
for i := 0; i < 10; i++ {
p := &UserProfile{Counter: i}
_, err := putVersioned(c, KindUserProfile, userkey, p)
if err != nil {
t.Fatal(err)
}
outputProfile := new(UserProfile)
err = getLatest(c, KindUserProfile, userkey, outputProfile)
if err != nil {
t.Fatal(err)
}
if outputProfile.Counter != i {
t.Fatalf("Expected Counter to be %d but it was %d", i, outputProfile.Counter)
}
}
}
func TestVersionedStorageAfterAllPuts(t *testing.T) {
c, err := aetest.NewContext(nil)
if err != nil {
t.Fatal(err)
}
userkey, err := datastore.Put(c, datastore.NewIncompleteKey(c, KindUser, nil), &User{})
if err != nil {
t.Fatal(err)
}
upper := 10
for i := 1; i <= upper; i++ {
p := &UserProfile{Counter: i}
_, err := putVersioned(c, KindUserProfile, userkey, p)
if err != nil {
t.Fatal(err)
}
}
outputProfile := new(UserProfile)
err = getLatest(c, KindUserProfile, userkey, outputProfile)
if err != nil {
t.Fatal(err)
}
if outputProfile.Counter != upper {
t.Fatalf("Expected Counter to be %d but it was %d", upper, outputProfile.Counter)
}
}
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