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@loopback/context
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@loopback/context - npm Package Compare versions
Comparing version 4.0.0-alpha.27 to 4.0.0-alpha.28
@@ -6,2 +6,10 @@ # Change Log | ||
| <a name="4.0.0-alpha.28"></a> | ||
| # [4.0.0-alpha.28](https://github.com/strongloop/loopback-next/compare/@loopback/context@4.0.0-alpha.27...@loopback/context@4.0.0-alpha.28) (2018-01-29) | ||
| **Note:** Version bump only for package @loopback/context | ||
| <a name="4.0.0-alpha.27"></a> | ||
@@ -8,0 +16,0 @@ # [4.0.0-alpha.27](https://github.com/strongloop/loopback-next/compare/@loopback/context@4.0.0-alpha.26...@loopback/context@4.0.0-alpha.27) (2018-01-26) |
| { | ||
| "name": "@loopback/context", | ||
| "version": "4.0.0-alpha.27", | ||
| "version": "4.0.0-alpha.28", | ||
| "description": "LoopBack's container for Inversion of Control", | ||
@@ -26,8 +26,8 @@ "engines": { | ||
| "dependencies": { | ||
| "@loopback/metadata": "^4.0.0-alpha.6", | ||
| "@loopback/metadata": "^4.0.0-alpha.7", | ||
| "debug": "^3.1.0" | ||
| }, | ||
| "devDependencies": { | ||
| "@loopback/build": "^4.0.0-alpha.10", | ||
| "@loopback/testlab": "^4.0.0-alpha.20", | ||
| "@loopback/build": "^4.0.0-alpha.11", | ||
| "@loopback/testlab": "^4.0.0-alpha.21", | ||
| "@types/bluebird": "^3.5.18", | ||
@@ -34,0 +34,0 @@ "@types/debug": "^0.0.30", |
| # @loopback/context | ||
| LoopBack uses Context to manage state and dependencies in your application. | ||
| This module provides facilities to manage artifacts and their dependencies using | ||
| `Context` in your Node.js applications. It can be used independent of the | ||
| LoopBack framework. | ||
| ## Overview | ||
| LoopBack implements the concept of a Context to represent a global registry in your application to manage config, state, dependencies, classes, etc. Context also serves as an IoC container used to inject dependencies into your code. | ||
| The `@loopback/context` package exposes TypeScript/JavaScript APIs and | ||
| decorators to register artifacts, declare dependencies, and resolve artifacts | ||
| by keys. The `Context` also serves as an [IoC container](https://en.wikipedia.org/wiki/Inversion_of_control) to support [dependency injection](https://en.wikipedia.org/wiki/Dependency_injection). | ||
| `Context` and `Binding` are the two core concepts. A context is a registry of | ||
| bindings and each binding represents a resolvable artifact by the key. | ||
| - Bindings can be fulfilled by a constant, a factory function, a class, or a | ||
| provider. | ||
| - Bindings can be grouped by tags and searched by tags. | ||
| - Binding scopes can be used to control how a resolved binding value is shared. | ||
| - Bindings can be resolved synchronously or asynchronously. | ||
| - Provide `@inject` and other variants of decorators to express dependencies. | ||
| - Support Constructor, property, and method injections. | ||
| - Allow contexts to form a hierarchy to share or override bindings. | ||
| - Track bindings and injections during resolution to detect circular dependencies. | ||
| ## Installation | ||
@@ -16,23 +33,50 @@ | ||
| ## Basic use | ||
| ### Locate an artifact by key | ||
| ```js | ||
| const Context = require('@loopback/context').Context; | ||
| const ctx = new Context(); | ||
| ctx.bind('hello').to('world'); // BindingKey='hello', BindingValue='world' | ||
| const helloVal = ctx.getSync('hello'); | ||
| console.log(helloVal); // => 'world' | ||
| ``` | ||
| The binding can also be located asynchronously: | ||
| ```ts | ||
| // app level | ||
| const app = new Application(); // `app` is a "Context" | ||
| app.bind('hello').to('world'); // ContextKey='hello', ContextValue='world' | ||
| console.log(app.getSync('hello')); // => 'world' | ||
| const helloVal = await ctx.get('hello'); | ||
| console.log(helloVal); // => 'world' | ||
| ``` | ||
| Dependency injection using context | ||
| ### Dependency injection using context | ||
| ```ts | ||
| const Application = require('@loopback/core'); | ||
| const app = new Application(); | ||
| app.bind('defaultName').to('John'); // setting context | ||
| import {Context, inject} from '@loopback/context'; | ||
| const ctx = new Context(); | ||
| // bind 'greeting' to 'Hello' as the constant value | ||
| ctx.bind('greeting').to('Hello'); | ||
| class HelloController { | ||
| // consider this.ctx here | ||
| constructor(@inject('defaultName') private name: string) { // injecting dependency using context | ||
| constructor( | ||
| // injecting the value bound to `greeting` using context | ||
| @inject('greeting') private greeting: string) { | ||
| } | ||
| greet(name) { | ||
| return `Hello ${name || this.name}`; | ||
| return `${this.greeting}, ${name}`; | ||
| } | ||
| } | ||
| // Bind 'HelloController' to class HelloController | ||
| ctx.bind('HelloController').toClass(HelloController); | ||
| async function hello() { | ||
| // Get an instance of HelloController | ||
| const helloController: HelloController = await ctx.get('HelloController'); | ||
| // helloController now has the `greeting` property injected with `Hello` | ||
| console.log(helloController.greet('John')); // => Hello, John | ||
| } | ||
| hello(); | ||
| ``` | ||
@@ -39,0 +83,0 @@ |
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