diff --git a/CHANGES.md b/CHANGES.md new file mode 100644 index 0000000..4468eeb --- /dev/null +++ b/CHANGES.md @@ -0,0 +1,7 @@ +Poodinis Changelog +================== +**Version 0.1** +* Initial open-source release +* ADD support for registering and resolving +* ADD registration scopes +* ADD autowiring diff --git a/README.md b/README.md new file mode 100644 index 0000000..a8269fe --- /dev/null +++ b/README.md @@ -0,0 +1,141 @@ +Poodinis Dependency Injection Framework +======================================= +Version 0.1 +Copyright 2014 Mike bierlee +Licensed under the terms of the MIT license - See [LICENSE.txt](LICENSE.txt) + +Poodinis is a dependency injection framework for the D programming language. It is inspired by the [Spring Framework] and [Hypodermic] IoC container for C++. Poodinis supports registering and resolving classes either by concrete type or interface. Automatic injection of dependencies is supported through the use of UDAs (Referred to as autowiring). + +Uses D 2.065.0 and Phobos. + +History +------- +For a full overview of changes, see [CHANGES.md](CHANGES.md) + +Getting started +--------------- +###DUB Dependency +Poodinis can be included in a project using [DUB]: +```json +... +"dependencies": { + "poodinis": "0.1" +} +... +``` +###Quickstart +The following example shows the typical usage of Poodinis: +```d +import poodinis.container; // The only import needed for now + +interface Database{}; +class RelationalDatabase : Database {} + +class DataWriter { + @Autowire + public Database database; // Automatically injected when class is resolved +} + +void main() { + auto container = Container.getInstance(); + container.register!DataWriter; + container.register!(Database, RelationalDatabase); + + auto writer = container.resolve!DataWriter; +} +``` + +### The container +To register a class, a new dependency container must be instantiated: +```d +// Register a private container +auto container = new Container(); +// Or use the singleton container +container = Container.getInstance(); +``` +###Registering dependencies +They make dependencies available, they have to be registered: +```d +// Register concrete class +container.register!ExampleClass; +// Register by interface +container.register!(ExampleInterface, ExampleClass); +``` +In the above example, dependencies on the concrete class and interface will resolve an instance of class ExampleClass. Registering a class by interface does not automatically register by concrete type. + +###Resolving dependencies +To manually resolve a dependency, all you have to do is resolve the dependency's type using the container in which it is registered: +```d +auto exampleClassInstance = container.resolve!ExampleClass; +``` +If the class is registered by interface and not by concrete type, you cannot resolve the class by concrete type. Registration of both a concrete type and interface type will resolve different registrations, returning different instances: + +```d +auto exampleClassInstance = container.resolve!ExampleClass; +auto exampleClassInstance2 = container.resolve!ExampleInterface; +assert(exampleClassInstance !is exampleClassInstance2); +``` + +###Dependency scopes +With dependency scopes, you can control how a dependency is resolved. The scope determines which instance is returned, be it the same each time or a new one. The following scopes are available: + +* Resolve a dependency using a single instance (default): + +```d +container.register!(ExampleClass).singleInstance(); +``` +* Resolve a dependency with a new instance each time it is resolved: + +```d +container.register!(ExampleClass).newInstance(); +``` +* Resolve a dependency using a pre-existing instance + +```d +auto preExistingInstance = new ExampleClass(); +container.register!(ExampleClass).existingInstance(preExistingInstance); +``` + +###Autowiring +The real value of any dependency injection framework comes from its ability to autowire dependencies. Poodinis supports autowiring by simply applying the **@Autowire** UDA to a member of a class: +```d +class ExampleClassA {} + +class ExampleClassB { + @Autowire + public ExampleClassA dependency; +} + +container.register!ExampleClassA; +auto exampleInstance = new ExampleClassB(); +container.autowire!ExampleClassB(exampleInstance); +assert(exampleInstance.dependency !is null); +``` +At the moment, it is only possible to autowire public members or properties. + +Dependencies are automatically autowired when a class is resolved. So when you register ExampleClassB, its member, *dependency*, is automatically injected: +```d +container.register!ExampleClassA; +container.register!ExampleClassB; +auto instance = container.resolve!ExampleClassB; +assert(instance.dependency !is null); +``` +If an interface is to be autowired, you must register a concrete class by interface. Any class registered by concrete type can only be injected when a dependency on a concrete type is autowired. + +###Circular dependencies +Poodinis can autowire circular dependencies to a certain degree. See known issues for current limitations on this. For now you might want to consider if your design really needs circular dependencies. + +Known issues +------------ +* Circular dependencies down the dependency tree still fails if the dependencies don't refer to the type being resolved initially. +* Due to preventive measures of recursion issues in circular dependencies, registrations which are supposed to yield new instances will not autowire classes for which a recursive resolve is detected. + +Future Work +----------- +* Thread safety +* Component scan (auto-registration) +* More robust detection and resolve of circular dependencies. + +[Spring Framework]: http://projects.spring.io/spring-framework/ +[Hypodermic]: https://code.google.com/p/hypodermic/ +[DUB]: http://code.dlang.org/