Error：Decorators are not valid here. 使用Angular中的装饰器

Decorators are not valid here，项目中出现这个提示信息，说明装饰器未知错误、或者在不支持的元素上使用了装饰器。
如下图所示，我在@NgModule装饰器后面加了一个导出方法，加完之后控制台提示了如下错误：Error TS1206：Decorators are not valid here.。@NgModule装饰器应该直接放在类定义之前，而代码中装饰器放在了方法前面，所以装饰器在这里无效：

修改对应位置的代码，@NgModule装饰器放在SharedModule前面，把getEcharts方法放在装饰器的前面或者类定义的后面，就好了：

在Angular中，装饰器是用来增强类、方法、属性和参数的强大工具。它们允许你添加元数据，改变行为，并使代码更具可读性和可维护性，在使用装饰器时，要知道使用了哪个装饰器，装饰器用在了哪个元素上。

常见的装饰器有下面几种，它们分别对应着一种使用情景

• @Component：定义一个组件

import { Component } from '@angular/core';

@Component({
  selector: 'app-my-component',
  templateUrl: './my-component.component.html',
  styleUrls: ['./my-component.component.css']
})
export class MyComponent {
  // ...
}

• @Directive：定义一个自定义指令

import { Directive, ElementRef } from '@angular/core';

@Directive({
  selector: '[appHighlight]'
})
export class HighlightDirective {
  constructor(private el: ElementRef) {
    el.nativeElement.style.backgroundColor = 'yellow';
  }
}

• @NgModule：定义一个Angular模块

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

• @Injectable：定义一个Angular服务

import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class MyService {
  // ...
}

• @Input：定义一个组件的输入属性

import { Component, Input } from '@angular/core';

@Component({
  // ...
})
export class MyComponent {
  @Input() name: string;
}

• @Output：定义一个组件的输出属性

import { Component, Output, EventEmitter } from '@angular/core';

@Component({
  // ...
})
export class MyComponent {
  @Output() onButtonClicked = new EventEmitter<any>();

  onClick() {
    this.onButtonClicked.emit('Button clicked!');
  }
}

• @HostListenter：鉴定宿主元素的事件

import { Directive, HostListener } from '@angular/core';

@Directive({
  selector: '[appClick]'
})
export class ClickDirective {
  @HostListener('click') onClick() {
    console.log('Click event!');
  }
}

• @HostBinding：绑定宿主元素的属性

import { Directive, HostBinding } from '@angular/core';

@Directive({
  selector: '[appHighlight]'
})
export class HighlightDirective {
  @HostBinding('style.backgroundColor') backgroundColor = 'yellow';
}

• @Pipe：定义一个Angular管道

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'capitalize'
})
export class CapitalizePipe implements PipeTransform {
  transform(value: string): string {
    return value.charAt(0).toUpperCase() + value.slice(1);
  }
}

• @ViewChild：获取模板中子组件的引用

import { Component, ViewChild } from '@angular/core';
import { MyComponent } from './my-component.component';

@Component({
  // ...
})
export class ParentComponent {
  @ViewChild(MyComponent) myComponent: MyComponent;

  // ...
}

• @ContentChild：获取模板中内容投影的引用

import { Component, ContentChild } from '@angular/core';
import { MyComponent } from './my-component.component';

@Component({
  // ...
})
export class ParentComponent {
  @ContentChild(MyComponent) myComponent: MyComponent;

  // ...
}

• @Inject：在依赖注入时指定要注入的依赖项

import { Injectable, Inject } from '@angular/core';
import { MY_TOKEN } from './my-token';

@Injectable({
  providedIn: 'root'
})
export class MyService {
  constructor(@Inject(MY_TOKEN) private myValue: string) {
    // ...
  }
}

• @Optional：在依赖注入时指定依赖项是可选的

import { Injectable, Inject, Optional } from '@angular/core';
import { MY_TOKEN } from './my-token';

@Injectable({
  providedIn: 'root'
})
export class MyService {
  constructor(@Optional() @Inject(MY_TOKEN) private myValue: string) {
    // ...
  }
}

• @SkipSelf：在依赖注入时跳过自身的提供者

import { Injectable, Inject, SkipSelf } from '@angular/core';
import { MY_TOKEN } from './my-token';

@Injectable({
  providedIn: 'root'
})
export class MyService {
  constructor(@SkipSelf() @Inject(MY_TOKEN) private myValue: string) {
    // ...
  }
}

• @Self：在依赖注入时只查找自身提供者

import { Injectable, Inject, Self } from '@angular/core';
import { MY_TOKEN } from './my-token';

@Injectable({
  providedIn: 'root'
})
export class MyService {
  constructor(@Self() @Inject(MY_TOKEN) private myValue: string) {
    // ...
  }
}

• @forwardRef：解决循环依赖问题

import { forwardRef, Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class AService {
  constructor(private bService: BService) {
    // ...
  }
}

@Injectable({
  providedIn: 'root'
})
export class BService {
  constructor(private aService: AService) {
    // ...
  }
}

import { forwardRef, Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class AService {
  constructor(private bService: BService) {
    // ...
  }
}

@Injectable({
  providedIn: 'root'
})
export class BService {
  constructor(@Inject(forwardRef(() => AService)) private aService: AService) {
    // ...
  }
}