Issue encountered in Angular 2 while attempting to import TypeScript classes using a single file

Upon loading my Angular 2 application, I encountered the following error:

EXCEPTION: Error: Uncaught (in promise): Unexpected piped value 'undefined' on the View of component 'DashboardComponent'

An interesting observation is that by uncommenting a specific line and removing the "CustomPipe" reference from "appCore", the application functions correctly again:

//import {CustomPipe} from "../shared/customPipe"

This situation raises questions about the correct importing and exporting of classes when utilizing the "parent" export file "appCore.ts," or if there might be an issue with Angular 2 itself.

Is there a mistake I am making in this setup?

Here is the Example Project on Github

CustomPipe.ts

import {Pipe, PipeTransform} from "angular2/core"

@Pipe({ name: "CustomPipe" })
export class CustomPipe implements PipeTransform
{
    constructor()
    {
        console.log("created");
    }
    public transform(value: string, args: any[]): string
    {
        return "this value has been transformed into me via a custom pipe";
    }
}

appCore.ts

export * from "./dashboard/dashboardComponent"
export * from "./vehicles/VehicleListComponent"
export * from "./vehicles/VehicleComponent"
export * from "./shared/nestedComponent"
export * from "./interfaces/IVehicleService"
export * from "./shared/staticVehicleService"
export * from "./shared/VehicleService"
export * from "./shared/customPipe"

dashboardComponent.ts

import {Component, Output, EventEmitter, OnInit, Inject, Injectable, provide, OpaqueToken} from "angular2/core"
import {CustomPipe, IVehicleService, StaticVehicleService} from "../appCore"
//import {CustomPipe} from "../shared/customPipe"
import {NestedComponent} from "../shared/nestedComponent"
import {Observable} from "rxjs/Rx"
import {IVehicleServiceToken} from "../interfaces/IVehicleService"

@Component({
    selector: "my-app",
    templateUrl: "./app/dashboard/dashboardComponent.html",
    styleUrls: ["./app/dashboard/dashboardComponent.css"],
    directives: [NestedComponent],
    pipes: [CustomPipe]
})
export class DashboardComponent implements OnInit
{
}  

Edit: Here is a Plunker showcasing the issue: Take a look at app/characters/character-list.component.ts line 5 & 6. The plunk will not work as intended initially, but if you uncomment line 6 and remove "CharacterService" from line 5, it will start functioning correctly.

Answer №1

Your code seems to be in good shape. I attempted to recreate it in my own app, but I couldn't reproduce the error you're experiencing.
It's possible that your Angular2 dependencies are outdated. I suggest updating all packages to their latest supported versions.

You can also check out a similar error discussed here, which may occur due to using incorrect npm dependency versions. Unexpected piped value 'undefined' on the View of component

Answer №2

Encountered a peculiar error with angular-2-0.0.rc4 lately. Oddly enough, repositioning my pipe import resolved the issue. Have you attempted adjusting your pipe import position?

It may seem illogical, but it did the trick for me.

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