clarify the relationship to remove must not be empty

README.md

@@ -394,6 +394,22 @@ For one to one relationships:
 err := store.RemoveThing(user)
 ```
 
+Note that for that to work, the thing you're deleting must **not** be empty. That is, you need to eagerly load (or set afterwards) the relationships.
+
+```go
+user, err := store.FindOne(NewUserQuery())
+checkErr(err)
+
+// THIS WON'T WORK! We've not loaded "Things"
+err := store.RemoveThings(user)
+
+user, err := store.FindOne(NewUserQuery().WithThings())
+checkErr(err)
+
+// THIS WILL WORK!
+err := store.RemoveThings(user)
+```
+
 ## Query models
 
 ### Simple queries

benchmarks/kallax.go

@@ -327,6 +327,9 @@ func (s *PersonStore) Transaction(callback func(*PersonStore) error) error {
 // RemovePets removes the given items of the Pets field of the
 // model. If no items are given, it removes all of them.
 // The items will also be removed from the passed record inside this method.
+// Note that is required that `Pets` is not empty. This method clears the
+// the elements of Pets in a model, it does not retrieve them to know
+// what relationships the model has.
 func (s *PersonStore) RemovePets(record *Person, deleted ...*Pet) error {
 	var updated []*Pet
 	var clear bool

generator/cli/kallax/cmd.go

@@ -8,7 +8,7 @@ import (
 	"gopkg.in/urfave/cli.v1"
 )
 
-const version = "1.2.18"
+const version = "1.2.19"
 
 func main() {
 	newApp().Run(os.Args)

generator/templates/model.tgo

@@ -62,7 +62,7 @@ func (r *{{.Name}}) SetRelationship(field string, rel interface{}) error {
                 {{else}}r.{{.Name}} = *val{{end}}
                 return nil
         {{else}}case "{{.Name}}":
-                records, ok := rel.([]kallax.Record) 
+                records, ok := rel.([]kallax.Record)
                 if !ok {
                         return fmt.Errorf("kallax: relationship field %s needs a collection of records, not %T", field, rel)
                 }
@@ -508,6 +508,9 @@ func (s *{{.StoreName}}) Transaction(callback func(*{{.StoreName}}) error) error
 // Remove{{.Name}} removes the given items of the {{.Name}} field of the
 // model. If no items are given, it removes all of them.
 // The items will also be removed from the passed record inside this method.
+// Note that is required that `{{.Name}}` is not empty. This method clears the
+// the elements of {{.Name}} in a model, it does not retrieve them to know
+// what relationships the model has.
 func (s *{{.Model.StoreName}}) Remove{{.Name}}(record *{{.Model.Name}}, deleted ...{{if $.IsPtrSlice .}}*{{end}}{{$.GenTypeName .}}) error {
         var updated []{{if $.IsPtrSlice .}}*{{end}}{{$.GenTypeName .}}
         var clear bool

tests/kallax.go

@@ -3956,6 +3956,9 @@ func (s *ParentStore) Transaction(callback func(*ParentStore) error) error {
 // RemoveChildren removes the given items of the Children field of the
 // model. If no items are given, it removes all of them.
 // The items will also be removed from the passed record inside this method.
+// Note that is required that `Children` is not empty. This method clears the
+// the elements of Children in a model, it does not retrieve them to know
+// what relationships the model has.
 func (s *ParentStore) RemoveChildren(record *Parent, deleted ...*Child) error {
 	var updated []*Child
 	var clear bool
@@ -4555,6 +4558,9 @@ func (s *ParentNoPtrStore) Transaction(callback func(*ParentNoPtrStore) error) e
 // RemoveChildren removes the given items of the Children field of the
 // model. If no items are given, it removes all of them.
 // The items will also be removed from the passed record inside this method.
+// Note that is required that `Children` is not empty. This method clears the
+// the elements of Children in a model, it does not retrieve them to know
+// what relationships the model has.
 func (s *ParentNoPtrStore) RemoveChildren(record *ParentNoPtr, deleted ...Child) error {
 	var updated []Child
 	var clear bool
@@ -5228,6 +5234,9 @@ func (s *PersonStore) Transaction(callback func(*PersonStore) error) error {
 // RemovePets removes the given items of the Pets field of the
 // model. If no items are given, it removes all of them.
 // The items will also be removed from the passed record inside this method.
+// Note that is required that `Pets` is not empty. This method clears the
+// the elements of Pets in a model, it does not retrieve them to know
+// what relationships the model has.
 func (s *PersonStore) RemovePets(record *Person, deleted ...*Pet) error {
 	var updated []*Pet
 	var clear bool
@@ -6670,6 +6679,9 @@ func (s *QueryFixtureStore) RemoveRelation(record *QueryFixture) error {
 // RemoveNRelation removes the given items of the NRelation field of the
 // model. If no items are given, it removes all of them.
 // The items will also be removed from the passed record inside this method.
+// Note that is required that `NRelation` is not empty. This method clears the
+// the elements of NRelation in a model, it does not retrieve them to know
+// what relationships the model has.
 func (s *QueryFixtureStore) RemoveNRelation(record *QueryFixture, deleted ...*QueryRelationFixture) error {
 	var updated []*QueryRelationFixture
 	var clear bool