2

我有一个常量，其他导入我的模块应该可以使用它。

我有 Datepicker 指令，它定义了日期格式常量（我有这样的，所以使用我的指令的人可以使用这些常量）：

export const DATETIME_FORMAT = 'DD/MM/YYYY HH:mm:ss';
export const DATE_FORMAT = 'DD/MM/YYYY';
export const TIME_FORMAT = 'DD/MM/YYYY';

NgModule 用于进一步导出它们。该模块被构建，然后在其他项目/模块中使用。

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { DatepickerDirective, TIME_FORMAT, DATETIME_FORMAT, DATE_FORMAT } from './datepicker.directive';

@NgModule({
  imports: [
    CommonModule
  ],
  exports: [
    DatepickerDirective,
    DATE_FORMAT,
    DATETIME_FORMAT,
    TIME_FORMAT
  ],
  declarations: [
    DatepickerDirective
  ]
})
export class DatepickerModule { }

但是在尝试构建它时，我得到了错误：

ERROR in src/app/datepicker/datepicker.module.ts(5,11): error TS2345: Argument of type '{ imports: (typeof CommonModule)[]; exports: (string | typeof DatepickerDirective)[]; declara...' is not assignable to parameter of type 'NgModule'.
  Types of property 'exports' are incompatible.
    Type '(string | typeof DatepickerDirective)[]' is not assignable to type '(any[] | Type<any>)[]'.
      Type 'string | typeof DatepickerDirective' is not assignable to type 'any[] | Type<any>'.
        Type 'string' is not assignable to type 'any[] | Type<any>'.
4

1 回答 1

5

NgModule不能导出常量，但你可以使用 InjectionToken 提供值。在此处查找有关InjectionToken 的更多信息。

import { ModuleWithProviders, NgModule, InjectionToken } from '@angular/core';
import { CommonModule } from '@angular/common';
import { DatepickerDirective, TIME_FORMAT, DATETIME_FORMAT, DATE_FORMAT } from './datepicker.directive';

export interface IDatepickerFormats {
  TIME_FORMAT: string;
  DATETIME_FORMAT: string;
  DATE_FORMAT: string;
}

export const DATEPICKER_FORMATS = new InjectionToken<IDatepickerFormats>('datepicker.formats');

@NgModule({
  imports: [CommonModule],
  exports: [DatepickerDirective],
  declarations: [DatepickerDirective]
})
export class DatepickerModule {
  static forRoot(): ModuleWithProviders {
    return {
      ngModule: DatepickerModule,
      providers: [
        {
          provide: DATEPICKER_FORMATS,
          useValue: {TIME_FORMAT, DATETIME_FORMAT, DATE_FORMAT}
        }
      ]
    };
  }
}

现在，每个导入Datepicker模块的模块都可以在其声明的组件中注入和使用这些常量。例如：

import { Component, Inject} from '@angular/core';
import { DATEPICKER_FORMATS, IDatepickerFormats } from './datepicker';

@Component({
  selector: 'app-example',
  templateUrl: './app-example.component.html',
  styleUrls: ['./app-example.component.scss']
})
export class AppExampleComponent {
  private DATE_FORMAT: string;
  private TIME_FORMAT: string;
  private DATETIME_FORMAT: string;

  constructor(@Inject(DATEPICKER_FORMATS) private datePickerFormats: IDatepickerFormats) {
    this.DATE_FORMAT = this.datePickerFormats.DATE_FORMAT;
    this.TIME_FORMAT = this.datePickerFormats.TIME_FORMAT;
    this.DATETIME_FORMAT = this.datePickerFormats.DATETIME_FORMAT;
  }
}
于 2018-01-26T16:36:36.447 回答