Add support for running queries that return void (#61)

README.md

@@ -126,8 +126,9 @@ For further examples take a look at the [example](https://github.com/vitusortner
 ## Querying
 Method signatures turn into query methods by adding the `@Query()` annotation with the query in parenthesis to them.
 Be patient about the correctness of your SQL statements.
-The are only partly validated while generating the code.
-These queries have to return an entity.
+They are only partly validated while generating the code.
+These queries have to return either a `Future` of an entity or `void`.
+Returning `Future<void>` comes in handy whenever you want to delete the full content of a table.
 
 ````dart
 @Query('SELECT * FROM Person WHERE id = :id')
@@ -138,6 +139,9 @@ Future<Person> findPersonByIdAndName(int id, String name);
 
 @Query('SELECT * FROM Person')
 Future<List<Person>> findAllPersons(); // select multiple items
+
+@Query('DELETE FROM person')
+Future<void> deleteAllPersons(); // query without returning an entity
 ````
 
 ## Persisting Data Changes
@@ -186,8 +190,7 @@ It's also required to add the `async` modifier. These methods can only return `F
 ```dart
 @transaction
 Future<void> replacePersons(List<Person> persons) async {
-  // execute SQL without automatically generated code
-  await database.execute('DELETE FROM Person');
+  await deleteAllPersons();
   await insertPersons(persons);
 }
 ```

floor_generator/lib/model/query_method.dart

@@ -64,6 +64,10 @@ class QueryMethod {
     return isList(type);
   }
 
+  bool get returnsVoid {
+    return method.returnType.flattenFutures(method.context.typeSystem).isVoid;
+  }
+
   Entity getEntity(final LibraryReader library) {
     final entity = _getEntities(library).firstWhere(
         (entity) => entity.displayName == flattenedReturnType.displayName,

floor_generator/lib/writer/query_method_writer.dart

@@ -20,7 +20,6 @@ class QueryMethodWriter implements Writer {
 
   Method _generateQueryMethod() {
     _assertReturnsFuture();
-    _assertReturnsEntity();
     _assertQueryParameters();
 
     return Method((builder) => builder
@@ -106,11 +105,14 @@ class QueryMethodWriter implements Writer {
   }
 
   String _generateMethodBody() {
-    final mapping = _generateMapping();
+    if (queryMethod.returnsVoid) {
+      return "await database.rawQuery('${queryMethod.query}');";
+    }
 
+    _assertReturnsEntity();
     return '''
     final rows = await database.rawQuery('${queryMethod.query}');
-    $mapping
+    ${_generateMapping()}
     ''';
   }
 

floor_test/test/database.dart

@@ -55,7 +55,7 @@ abstract class TestDatabase extends FloorDatabase {
 
   @transaction
   Future<void> replacePersons(List<Person> persons) async {
-    await database.execute('DELETE FROM person');
+    await deleteAllPersons();
     await insertPersons(persons);
   }
 
@@ -67,6 +67,9 @@ abstract class TestDatabase extends FloorDatabase {
 
   @Query('SELECT * FROM dog')
   Future<List<Dog>> findAllDogs();
+
+  @Query('DELETE FROM person')
+  Future<void> deleteAllPersons();
 }
 
 @Entity(tableName: 'person')
@@ -77,6 +80,9 @@ class Person {
   @ColumnInfo(name: 'custom_name', nullable: false)
   final String name;
 
+//  @embedded
+//  final Address address;
+
   Person(this.id, this.name);
 
   @override
@@ -135,3 +141,26 @@ class Dog {
     return 'Dog{id: $id, name: $name, ownerId: $ownerId}';
   }
 }
+
+class Address {
+  final String street;
+  final String city;
+
+  Address(this.street, this.city);
+
+  @override
+  bool operator ==(Object other) =>
+      identical(this, other) ||
+      other is Address &&
+          runtimeType == other.runtimeType &&
+          street == other.street &&
+          city == other.city;
+
+  @override
+  int get hashCode => street.hashCode ^ city.hashCode;
+
+  @override
+  String toString() {
+    return 'Address{street: $street, city: $city}';
+  }
+}

floor_test/test/database_test.dart

@@ -198,6 +198,18 @@ void main() {
         expect(actual, isEmpty);
       });
     });
+
+    group('query with void return', () {
+      test('delete all persons', () async {
+        final persons = [Person(1, 'Simon'), Person(2, 'Frank')];
+        await database.insertPersons(persons);
+
+        await database.deleteAllPersons();
+        final actual = await database.findAllPersons();
+
+        expect(actual, isEmpty);
+      });
+    });
   });
 }