Angular 2构造函数注入与直接访问 [英] Angular 2 constructor injection vs direct access
问题描述
Q1。我有一个带有一些实用程序/帮助程序方法的通用实用程序类(没有获取/发布请求)。我首先要问的是,它应该是简单的类还是 @Injectable
类。因为两者都可以在导入这样的任何组件类之后使用
Q1. I have a common utility class with some utility/helper methods (no get/post request). First thing I have to ask is that whether it should be a simple class or an @Injectable
class. Because both can be used after importing in any component class like this
import { Injectable } from '@angular/core';
Injectable()
export class Utils {
}
OR
export class Utils {
}
第二季度。如果它是可注入的,那么我必须将其导入到我的组件类中,注入到构造函数中,并且必须添加providers数组,然后我可以使用注入的类/服务的任何方法,例如
Q2. If it's injectable then I have to import this in my component class, inject in the constructor, and must have to add in providers array then I can use any method of the injected class/service like
import { Utils } from './../shared/utils';
@Component({
moduleId: module.id,
selector: 'abc',
templateUrl: './abc.component.html',
providers: [Utils]
})
export class DemoComponent implements OnInit {
constructor(private _u: Utils) { }
ngOnInit(): void {
this._u.someMethod();
}
}
但是除此之外,我可以直接访问服务方法而无需构造函数注入,而无需添加提供程序,这是一个简短的方法,例如
But beside this I can directly access the service methods without constructor injection and without having to add in providers, which is a short way like
import { Utils } from './../shared/utils';
@Component({
moduleId: module.id,
selector: 'abc',
templateUrl: './abc.component.html'
})
export class DemoComponent implements OnInit {
constructor() { }
ngOnInit(): void {
Utils.someMethod();
}
}
所以我想知道哪个更好,建议
So I wanted to know which one is better and recommended approach?
推荐答案
在构造函数中使用它时,
When you are using it in constructor,
- 您在整个组件中使用服务的单独实例。
-
用作Injectable()时,应在提供者内部声明该模块的数组。
constructor(private _u: Utils) { }
ngOnInit(): void {
this._u.someMethod();
}
//private - _u => is specific inside this component
如果是直接访问,资源将按原样使用,这可能会导致以下问题
In case of direct access, the resources are used as it is which might create following problems
- 内存泄漏
- 较少可重用性
- 对于可观察性,在取消可观察性之前,您无法再次订阅。
这篇关于Angular 2构造函数注入与直接访问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IT屋!