NullInjectorError: No provider for SlicePipe

Question

我创建了自定义 pipe，它使用另一个内置 pipe 这是示例：

import { Pipe, PipeTransform } from '@angular/core';
import { SlicePipe } from '@angular/common';
import { isNumeric } from 'rxjs/util/isNumeric';

@Pipe({ name: 'range' })
export class RangePipe implements PipeTransform {
    constructor(private slicePipe: SlicePipe) { }

    transform(data: any, page: number, size: number): any {
        if (Array.isArray(data) && isNumeric(page) && isNumeric(size)) {
            const start_index = (page - 1) * size;
            if (data.length < start_index) {
                return [];
            } else {
                return this.slicePipe.transform(data.slice(start_index), size);
            }
        } else {
            return data;
        }
    }
}

还将我的自定义 pipe 添加到 app.module

@NgModule({
imports: [
    BrowserModule,
    FormsModule,
    routing
],
declarations: [
    AppComponent,
    ...
    RangePipe
],
providers: [],
bootstrap: [AppComponent]
})

但是报错

ERROR Error: Uncaught (in promise): Error: StaticInjectorError(AppModule)[RangePipe -> SlicePipe]: StaticInjectorError(Platform: core)[RangePipe -> SlicePipe]: NullInjectorError: No provider for SlicePipe!

我的问题在哪里？我是不是忘记注册了？

Answer 1

假设您需要在 angular DI 中使用自定义 class。

import {FactoryProvider} from "@angular/core";
import {SlicePipe} from "@angular/common";

class AwesomePipe{
  constructor(private slicePipe: SlicePipe){

  }
}

这取决于其他一些 classes

class AwesomeClassProvider implements FactoryProvider{ 
  provide: AwesomePipe;
  useFactory(pipe: SlicePipe) {
    return new AwesomePipe(pipe);  
  }
  deps: [SlicePipe]
}

Answer 2

只是扩展了 SlicePipe

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

import { SlicePipe } from '@angular/common';
import { isNumeric } from 'rxjs/util/isNumeric';

@Pipe({ name: 'range' })
export class RangePipe extends SlicePipe implements PipeTransform {
    public transform(data: any, page: number, size: number): any {
        if (Array.isArray(data) && isNumeric(page) && isNumeric(size)) {
            const start_index = (page - 1) * size;
            if (data.length < start_index) {
                return [];
            } else {
                return super.transform(data.slice(start_index), size);
            }
        } else {
            return data;
        }
    }
}

希望对您有所帮助。

Answer 3

@NgModule({
imports: [
    ...
],
declarations: [
    ...
],
providers: [RangePipe],
bootstrap: [AppComponent]
})

NullInjectorError: No provider for SlicePipe

NullInjectorError: No provider for SlicePipe

javascript

typescript

angular-pipe

angular