Angular2: custom pipe could not be found

问题

The built-in pipe is work,but all custom pipes that i wanna use are the same error:

the pipe 'actStatusPipe' could not be found

[ERROR ->]{{data.actStatus | actStatusPipe}}

I have tried two ways,declare it in app.module's declarations:

app.module.ts:

import {ActStatusPipe} from '../pipe/actPipe'

@NgModule({
    declarations: [
        AppComponent,
        HomePage,
        ActivitiesList,
        ActStatusPipe
    ],
    ...
})

or use other module to declare and export all my pipes: //pipe

import {ActStatusPipe} from "./actPipe"

@NgModule({
    declarations:[ActStatusPipe],
    imports:[CommonModule],
    exports:[ActStatusPipe]
})

export class MainPipe{}

and import it in app.module.

//pipe
import {MainPipe} from '../pipe/pipe.module'

@NgModule({
    declarations:[...],
    imports:[...,MainPipe],
})

But none of them work in my app.

Here is my code of the pipe:

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

@Pipe({
    name:'actStatusPipe'
})
export class ActStatusPipe implements PipeTransform{
    transform(status:any):any{
        switch (status) {
            case 1:
                return "UN_PUBLISH";
            case 2:
                return "PUBLISH";
            default:
                return status
        }
    }
}

I think it is most of the same with the document(In fact,i have just copied from the document and made a little modification)

And my angular2's version is 2.1.

Lots of solution that can be searched in stackOverflow and google are tried in my app,however they don't work.

This confused me a lot,thanks for you answer!

回答1:

see this is working for me.

ActStatus.pipe.ts First this is my pipe

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

@Pipe({
  name:'actStatusPipe'
})
export class ActStatusPipe implements PipeTransform{
  transform(status:any):any{
    switch (status) {
      case 1:
        return "UN_PUBLISH";
      case 2:
        return "PUBLISH";
      default:
        return status
    }
  }
}

main-pipe.module.ts in pipe module, i need to declare my pipe/s and export it.

import { NgModule } from '@angular/core';
import {CommonModule} from "@angular/common";

import {ActStatusPipe} from "./ActStatusPipe.pipe"; // <---

@NgModule({
  declarations:[ActStatusPipe], // <---
  imports:[CommonModule],
  exports:[ActStatusPipe] // <---
})

export class MainPipe{}

app.module.ts user this pipe module in any module.

@NgModule({
  declarations: [...],
  imports: [..., MainPipe], // <---
  providers: [...],
  bootstrap: [AppComponent]
})

you can directly user pipe in this module. but if you feel that your pipe is used with in more than one component i suggest you to follow my approach.

1. create pipe .
2. create separate module and declare and export one or more pipe.
3. user that pipe module.

How to use pipe totally depends on your project complexity and requirement. you might have just one pipe which used only once in the whole project. in that case you can directly use it without creating a pipe/s module (module approach).

回答2:

This didnt worked for me. (Im with Angular 2.1.2). I had NOT to import MainPipeModule in app.module.ts and importe it instead in the module where the component Im using the pipe is imported too.

Looks like if your component is declared and imported in a different module, you need to include your PipeModule in that module too.

回答3:

import {CommonModule} from "@angular/common";

Adding this statement to the pipe module solved my problem.

回答4:

If you are declaring your pipe in another module, make sure to add it to that module Declarations and Exports array, then import that module in whatever module is consuming that pipe.

回答5:

be sure, that if the declarations for the pipe are done in one module, while you are using the pipe inside another module, you should provide correct imports/declarations at the current module under which is the class where you are using the pipe. In my case that was the reason for the pipe miss

来源：https://stackoverflow.com/questions/40457744/angular2-custom-pipe-could-not-be-found