injector constructors

lib/dependencies.dart

@@ -1,6 +1,7 @@
 /// Dependency injection container for dart.
 library dependencies;
 
+import 'package:meta/meta.dart';
 import 'package:quiver/check.dart';
 import 'package:quiver/core.dart';
 import 'package:disposables/disposables.dart';
@@ -14,6 +15,7 @@ part 'src/builder/_injector_builder_container.dart';
 part 'src/builder/injector_builder.dart';
 part 'src/injector/_injector_base.dart';
 part 'src/injector/_injector_container.dart';
+part 'src/injector/_empty_injector.dart';
 part 'src/injector/error.dart';
 part 'src/injector/injector.dart';
 part 'src/params/params.dart';

lib/src/builder/_injector_builder_container.dart

@@ -17,7 +17,9 @@ class _InjectorBuilderContainer extends _BinderContainer
 
   @override
   Injector build() {
-    return _InjectorContainer(_clone(), name: name);
+    return registrations.isNotEmpty
+      ? _InjectorContainer(_clone(), name: name)
+      : _EmptyInjector(name: name);
   }
 
   _InjectorBuilderContainer _clone() {

lib/src/builder/injector_builder.dart

@@ -2,10 +2,6 @@ part of 'package:dependencies/dependencies.dart';
 
 /// Builder to create [Injector] instances.
 abstract class InjectorBuilder implements Binder {
-  factory InjectorBuilder() {
-    return _InjectorBuilderContainer();
-  }
-
   /// Sets the name of the injector.
   void setName(String name);
 

lib/src/injector/_empty_injector.dart

@@ -0,0 +1,29 @@
+part of 'package:dependencies/dependencies.dart';
+
+class _EmptyInjector extends Object with DisposableMixin implements Injector {
+  @override
+  final String name;
+  @override
+  final Iterable<Binding> bindings = const [];
+
+  _EmptyInjector({String name}):
+      this.name = _nameOrDefault(name);
+
+  @override
+  bool contains<T>({String name}) => false;
+
+  @override
+  T get<T>({String name, Params params}) {
+    throw InjectionException._internal("Can't get instance from empty injector");
+  }
+
+  @override
+  Optional<T> getOptional<T>({String name, Params params}) {
+    return Optional.absent();
+  }
+
+  @override
+  void doDispose() {
+  }
+
+}

lib/src/injector/injector.dart

@@ -1,8 +1,5 @@
 part of 'package:dependencies/dependencies.dart';
 
-/// A function to set up bindings.
-typedef void BinderFunc(Binder binder);
-
 String _nameOrDefault(String name) => name ?? "injector";
 
 /// Dependency injection container.
@@ -30,16 +27,34 @@ abstract class Injector implements Disposable {
   void dispose();
 
   /// Creates an [Injector] from it's bindings.
-  factory Injector(BinderFunc binderFunc, {String name}) {
-    checkNotNull(binderFunc, message: () => "binderFunc can't be null");
+  factory Injector({@required BindFunc bindFunc, String name}) {
+    checkNotNull(bindFunc, message: () => "bindFunc can't be null");
     final b = builder();
-    if (name != null) b.setName(name);
-    binderFunc(b);
+    if (name == null) b.setName(name);
+    bindFunc(b);
     return b.build();
   }
 
+  /// Creates an empty [Injector].
+  factory Injector.empty({String name}) {
+    return _EmptyInjector();
+  }
+
+  /// Creates an [Injector] from a [Module].
+  factory Injector.fromModule({@required Module module, String name}) {
+    checkNotNull(module, message: () => "module can't be null");
+    return Injector(name: name, bindFunc: (bind) => bind.install(module));
+  }
+
+  /// Creates an [Injector] from a list of [Module] instances.
+  factory Injector.fromModules(
+      {@required Iterable<Module> modules, String name}) {
+    checkNotNull(modules, message: () => "modules can't be null");
+    return Injector.fromModule(name: name, module: Module.compose(modules));
+  }
+
   /// Creates a [InjectorBuilder] to create [Injector] instances.
   static InjectorBuilder builder() {
-    return InjectorBuilder();
+    return _InjectorBuilderContainer();
   }
 }

pubspec.yaml

@@ -8,7 +8,7 @@ environment:
   sdk: '>=2.0.0 <3.0.0'
 
 dependencies:
-  quiver: ^2.0.1
+  quiver: ^2.0.2
   disposables: ^0.0.1
 
 dev_dependencies:

test/src/builder/injector_builder_test.dart

@@ -60,10 +60,8 @@ void main() {
   });
 }
 
-typedef void _BuilderFunc(InjectorBuilder builder);
-
-Injector _newInjector([_BuilderFunc func]) {
-  final builder = InjectorBuilder();
+Injector _newInjector([BindFunc func]) {
+  final builder = Injector.builder();
   if (func != null) func(builder);
   return builder.build();
 }