Angular2：找不到自定义管道

Question

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!

Answer 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).

Answer 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.

Answer 3

A really dumb answer (I'll vote myself down in a minute), but this worked for me:

After adding your pipe, if you're still getting the errors and are running your Angular site using " ng serve ", stop it... then start it up again.

For me, none of the other suggestions worked, but simply stopping, then restarting " ng serve " was enough to make the error go away.

Strange.

Answer 4

I take no issue with the accepted answer as it certainly helped me. However, after implementing it, I still got the same error.

Turns out this was because I was calling the pipes incorrectly in my component as well:

My custom-pipe.ts file:

@Pipe({ name: 'doSomething' })
export class doSomethingPipe implements PipeTransform {
    transform(input: string): string {
        // Do something
    }
}

So far, so good, but in my component.html file I was calling the pipes as follows:

{{ myData | doSomethingPipe }}

This will again throw the error that the pipe is not found. This is because Angular looks up the pipes by the name defined in the Pipe decorator. So in my example, the pipe should instead be called like this:

{{ myData | doSomething }}

Silly mistake, but it cost me a fair amount of time. Hope this helps!

Answer 5

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

将此语句添加到管道模块解决了我的问题。

Answer 6

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

Answer 7

Also make sure your pipe name (inside the decorator) is v̲i̲s̲i̲b̲l̲y camelCased.

This does not work : @Pipe({ name: 'plural' }) ❌,
but this does : @Pipe({ name: 'pluralForm' }) ✅

Answer 8

如果您要在另一个模块中声明管道，请确保将其添加到该模块的声明和导出数组中，然后将该模块导入到使用该管道的任何模块中。

Answer 9

I encountered a similar issue, but putting it in my page's module didn't work.

I had created a component, which needed a pipe. This component was declared and exported in a ComponentsModule file, which holds all of the app's custom components.

I had to put my PipesModule in my ComponentsModule as an import, in order for these components to use these pipes and not in the page's module using that component.

Credits: enter link description here Answer by: tumain

Answer 10

I faced similar issue.Mine got resolved by :-

1. Importing the pipe's module(SharedModule) into the required module.
2. Add the custom pipe in the providers array. @NgModule({ imports: [ SharedModule ], providers: [CustomPipe] )}

Answer 11

Please make sure you're using the 'selector' while using th pipe. for eg:

import { Pipe, PipeTransform } from '@angular/core';
@Pipe({
  name: 'removeApos'
})
export class RemoveAposPipe implements PipeTransform {
  transform(value: unknown, ...args: unknown[]): unknown {
    return null;
  }
}

you need to use this as

<div>{{someval | removeApos}}</div>

please note the selector in the above eg and its usage in the div