Merge pull request #127 from erizocosmico/feature/store-from

implement StoreFrom function to transmute stores

Author: Miguel Molina

README.md

@@ -572,11 +572,12 @@ store.Transaction(func(s *UserStore) error {
 })
 ```
 
-The fact that a transaction receives a store with the type of the model can be a problem if you want to store several models of different types. You can, indeed, create new stores of the other types, but do so with care. Do not use the internal `*kallax.Store`, as it does not perform any type checks or some of the operations the concrete type stores do.
+The fact that a transaction receives a store with the type of the model can be a problem if you want to store several models of different types. Kallax has a method named `StoreFrom` that initializes a store of the type you want to have the same underlying store as some other.
 
 ```go
 store.Transaction(func(s *UserStore) error {
-        postStore := &PostStore{s.Store}
+        var postStore PostStore
+        kallax.StoreFrom(&postStore, s)
 
         for _, p := range posts {
                 if err := postStore.Insert(p); err != nil {

generator/templates/model.tgo

@@ -96,6 +96,16 @@ func New{{.StoreName}}(db *sql.DB) *{{.StoreName}} {
 	return &{{.StoreName}}{kallax.NewStore(db)}
 }
 
+// GenericStore returns the generic store of this store.
+func (s *{{.StoreName}}) GenericStore() *kallax.Store {
+        return s.Store
+}
+
+// SetGenericStore changes the generic store of this store.
+func (s *{{.StoreName}}) SetGenericStore(store *kallax.Store) {
+        s.Store = store
+}
+
 {{if .HasNonInverses}}
 func (s *{{.StoreName}}) relationshipRecords(record *{{.Name}}) []kallax.RecordWithSchema {
         var records []kallax.RecordWithSchema

store.go

@@ -33,6 +33,24 @@ var (
 	ErrCantSetID = errors.New("kallax: model does not have an auto incrementable primary key, it needs to implement IDSetter interface")
 )
 
+// GenericStorer is a type that contains a generic store and has methods to
+// retrieve it and set it.
+type GenericStorer interface {
+	// GenericStore returns the generic store in this type.
+	GenericStore() *Store
+	// SetGenericStore sets the generic store for this type.
+	SetGenericStore(*Store)
+}
+
+// StoreFrom sets the generic store of `from` in `to`.
+func StoreFrom(to, from GenericStorer) {
+	if to == nil || from == nil {
+		return
+	}
+
+	to.SetGenericStore(from.GenericStore())
+}
+
 // Store is a structure capable of retrieving records from a concrete table in
 // the database.
 type Store struct {

store_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 
 	_ "github.com/lib/pq"
+	"github.com/stretchr/testify/require"
 	"github.com/stretchr/testify/suite"
 )
 
@@ -526,3 +527,26 @@ func (s *StoreSuite) assertNotExists(m *model) {
 func TestStore(t *testing.T) {
 	suite.Run(t, new(StoreSuite))
 }
+
+type store1 struct {
+	*Store
+}
+
+func (s *store1) GenericStore() *Store {
+	return s.Store
+}
+
+func (s *store1) SetGenericStore(store *Store) {
+	s.Store = store
+}
+
+func TestStoreFrom(t *testing.T) {
+	var s1 = &store1{new(Store)}
+	var s2 store1
+
+	require := require.New(t)
+	require.NotEqual(s1.Store, s2.Store)
+
+	StoreFrom(&s2, s1)
+	require.Exactly(s1.Store, s2.Store)
+}