typescript:使用注入参数隐式调用构造函数
如何以这种方式创建点的实例:typescript:使用注入参数隐式调用构造函数,typescript,dependency-injection,constructor,angular5,Typescript,Dependency Injection,Constructor,Angular5,如何以这种方式创建点的实例: let npoint = new Point(); Point的构造函数需要一个参数(不同),该参数应该被注入 import { DoCheck, KeyValueDiffers, KeyValueDiffer } from '@angular/core'; export class GsPoint { uuid: string; differ: any; constructor(private differs: KeyValueDiffers)
let npoint = new Point();
Point的构造函数需要一个参数(不同),该参数应该被注入
import { DoCheck, KeyValueDiffers, KeyValueDiffer } from '@angular/core';
export class GsPoint {
uuid: string;
differ: any;
constructor(private differs: KeyValueDiffers) {
this.differ = this.differs.find({}).create();
}
ngDoCheck() {
const change = this.differ.diff(this);
if (change) {
change.forEachChangedItem(item => {
console.log('item changed', item);
});
}
}
}
如果它是一个普通类(不是组件或指令),那么您不能像我们在组件级别或模块级别那样注入
keyvaluedifferents
服务
1)你需要
- 将@Injectable()添加到GsPoint并
- 在组件或模块中提供类似GsPoint的提供程序:[GsPoint]
constructor(private injector:Injector) {
let resolvedProviders = ReflectiveInjector.resolve([KeyValueDiffers]);
let childInjector = ReflectiveInjector.fromResolvedProviders(resolvedProviders,this.injector);
let myDiffer : KeyValueDiffers= childInjector.get(KeyValueDiffers);
}
这样,mydifferent
将是一个由Angulars DI实例化的KeyValueDifferences
实例,并且当实例化时,mydifference
将被注入到GSPoint
中
但是,如果您希望以这种方式执行此操作,那么在组件或服务中,无论您在哪里使用此类,都必须传递this.mydifferent
的keyvaluedifferences
实例。(注意:-keyvaluedifferences
必须注入到创建此GsPoint类对象的组件中)
}您描述的是某种服务定位器。 一般来说,我不建议使用这种方法,因为您对调用方隐藏了类依赖项,这可能会使测试更加困难
import {KeyValueDiffers , Component } from '@angular/core';
import {GSPoint} from '../gspoint/gspoint.ts';
@Component({
'selector': 'app-sample',
'templateUrl':'sample.html',
'styleUrl': 'sample.css'
})
export class Sample {
constructor(private diff: KeyValueDiffers){
}
ngOnInit(){
let gsPoint = new GSPoint(this.dff); // this is how you can create object
}