问题描述
我正在 angularjs 2.0 中创建一个示例应用程序.在开发过程中，我遇到了一个严重的问题 - 我无法通过构造函数向组件注入任何内容.
I am creating a sample application in angularjs 2.0. While developement I came across with a serious problem - I can't inject anything to the component through the constructor function.
这是 plnkr 网址:https://plnkr.co/edit/g1UcGmYPLtY8GiXuNHzK?p=预览
This is the plnkr url : https://plnkr.co/edit/g1UcGmYPLtY8GiXuNHzK?p=preview
我使用以下代码从 app.item.service.ts 导入 ItemService
I used the following code for importing ItemService from app.item.service.ts
import { ItemService } from './app.item.service';
然后我将提供者指定为
@Component({
selector: 'list-todo',
template: `
<ul>
<li *ngFor="let item of items">{{item.text}}</li>
</ul>
`,
providers : [ItemService]
})
之后，给定 TodoComponent 的代码为
After that, given code for TodoComponent as
export class TodoComponent implements OnInit {
items:Array<Object> = [];
constructor(private itemService: ItemService){ //here is the problem
}
ngOnInit(){
this.getItems();
}
getItems(){
this.items = this.itemService.getItems();
}
}
当我尝试通过构造函数注入 ItemService 时，出现错误:错误:无法解析 TodoComponent 的所有参数:(?)."我什至无法注入像 Injector 这样的 angularjs 提供程序.
When I try to inject ItemService through constructor , I am getting an error : " Error: Can't resolve all parameters for TodoComponent: (?)."I am not able to inject even angularjs providers like Injector.
但是，这个方法对我有用:
However, this method works for me :
const injector = ReflectiveInjector.resolveAndCreate([ItemService]);
this.itemService = injector.get(ItemService);
如我的 package.json 中所述，我正在使用以下版本的库进行开发
I am using the following versions of libraries for developement as mentioned in my package.json
"dependencies": {
"@angular/common": "2.0.0",
"@angular/compiler": "2.0.0",
"@angular/core": "2.0.0",
"@angular/forms": "2.0.0",
"@angular/http": "2.0.0",
"@angular/platform-browser": "2.0.0",
"@angular/platform-browser-dynamic": "2.0.0",
"@angular/router": "3.0.0",
"@angular/upgrade": "2.0.0",
"core-js": "^2.4.1",
"reflect-metadata": "^0.1.3",
"rxjs": "5.0.0-beta.12",
"systemjs": "0.19.27",
"zone.js": "^0.6.23",
"angular2-in-memory-web-api": "0.0.20",
"bootstrap": "^3.3.6"
},
"devDependencies": {
"concurrently": "^2.2.0",
"lite-server": "^2.2.2",
"typescript": "^2.0.2",
"typings":"^1.3.2"
}
- Angular 版本:2.0.0 最终版
- 浏览器:所有
附上我从控制台得到的错误日志:
attaching the error log I got from console :
(index):16 Error: Error: Can't resolve all parameters for TodoComponent: (?).
at CompileMetadataResolver.getDependenciesMetadata (http://localhost:3000/node_modules/@angular/compiler/bundles/compiler.umd.js:14404:21)
at CompileMetadataResolver.getTypeMetadata (http://localhost:3000/node_modules/@angular/compiler/bundles/compiler.umd.js:14301:28)
at CompileMetadataResolver.getDirectiveMetadata (http://localhost:3000/node_modules/@angular/compiler/bundles/compiler.umd.js:14074:30)
at eval (http://localhost:3000/node_modules/@angular/compiler/bundles/compiler.umd.js:14167:51)
at Array.forEach (native)
at CompileMetadataResolver.getNgModuleMetadata (http://localhost:3000/node_modules/@angular/compiler/bundles/compiler.umd.js:14161:51)
at RuntimeCompiler._compileComponents (http://localhost:3000/node_modules/@angular/compiler/bundles/compiler.umd.js:16803:49)
at RuntimeCompiler._compileModuleAndComponents (http://localhost:3000/node_modules/@angular/compiler/bundles/compiler.umd.js:16741:39)
at RuntimeCompiler.compileModuleAsync (http://localhost:3000/node_modules/@angular/compiler/bundles/compiler.umd.js:16732:23)
at PlatformRef_._bootstrapModuleWithZone (http://localhost:3000/node_modules/@angular/core/bundles/core.umd.js:6954:29)
Evaluating http://localhost:3000/dist/main.js
Error loading http://localhost:3000/dist/main.js(anonymous function) @ (index):16ZoneDelegate.invoke @ zone.js:203Zone.run @ zone.js:96(anonymous function) @ zone.js:462ZoneDelegate.invokeTask @ zone.js:236Zone.runTask @ zone.js:136drainMicroTaskQueue @ zone.js:368ZoneTask.invoke @ zone.js:308
推荐答案
我发现您的 tsconfig.json 不正确.
I see that your tsconfig.json isn't correct.
{
"compilerOptions": {
"target": "es5",
"module": "commonjs",
"moduleResolution": "node",
"sourceMap": false,
"emitDecoratorMetadata": true, <== it should be true
"experimentalDecorators": true,
"removeComments": false,
"noImplicitAny": false,
"outDir": "dist"
}
}
这是 DI 的魔法酱.emitDecoratorMetadata:真.此选项将保留对象元数据中的类型信息.
This is the magic sauce for DI. emitDecoratorMetadata: true. This option will preserve type information in your object's metadata.
另见
这篇关于angularjs 2.0:无法通过组件构造函数()注入任何内容的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！