截至Angular v2.0,inheritance is supported between components.
给定父类,通过依赖注入向构造函数提供服务,是否可以定义扩展(或继承)其父类的子类,以便它可以访问父服务？
import {MyService} from './my.service'
import {OnInit} from '@angular/core'
@Component({
selector: 'parent-selector',providers: [MyService],templateUrl: 'my_template.html'
})
export class ParentClass implements OnInit{
public foobar: number;
constructor(protected _my_service: MyService){};
ngOnInit(){
foobar = 101;
}
}
@Component({
selector: 'child-selector',templateUrl: 'my_template.html'
})
export class ChildClass extends ParentClass{
public new_child_function(){
// This prints successfully
console.log(this.foobar);
// This throws an error saying my_service is "undefined"
this._my_service.service_function();
}
}
当我们尝试从子类调用new_child_function()时,它会成功访问其父成员foobar,但是对this._my_service.service_function()的调用会给我们带来以下不那么有趣的错误：
Cannot read property 'get' of undefined
在这种特定情况下,孩子看不到父母注射的服务.我想知道：
>这是Angular2的组件继承支持的当前已知限制吗？
>此代码示例是否缺少/错误？
>这是Angular2对组件继承的支持的错误吗？
解决方法
公开或保护,即
constructor(protected _my_service: MyService){};
if you do not use in the constructor
protected,private,orpublic,for example,DI,the range of the variable_my_serviceis the scope of theconstructor { }you could not use from another function.
您可以阅读有关Parameter properties以及如何声明和访问它们的更多信息.
Parameter properties are declared by prefixing a constructor parameter with an accessibility modifier or
readonly,or both.
