Angular 2 component is not a known element

Question

I m trying to use a component I created inside the AppModule in other modules  I get the following error though       Uncaught  in promise   Error  Template parse errors        contacts-box  is not a known element          If  contacts-box  is an Angular component  then verify that it is part of this module    If  contacts-box  is a Web Component then add  CUSTOM ELEMENTS SCHEMA  to the   NgModule schemas  of this component to suppress this message       My project structure is quite simple    I keep my pages in pages directory  where each page is kept in different module  e g  customers-module  and each module has multiple components  like customers-list-component  customers-add-component and so on   I want to use my ContactBoxComponent inside those components  so inside customers-add-component for example    As you can see I created the contacts-box component inside the widgets directory so it s basically inside the AppModule  I added the ContactBoxComponent import to app module ts and put it in declarations list of AppModule  It didin t work so I googled my problem and added ContactBoxComponent to export list as well  Didn t help  I also tried putting ContactBoxComponent in CustomersAddComponent and then in another one  from different module  but I got an error saying there are multiple declarations   What am I missing

User · Answer

I had a similar issue  It turned out that ng generate component  using CLI version 7 1 4  adds a declaration for the child component to the AppModule  but not to the TestBed module that emulates it   The  Tour of Heroes  sample app contains a HeroesComponent with selector app-heroes   The app ran fine when served  but ng test produced this error message   app-heroes  is not a known element  Adding the HeroesComponent manually to the declarations in configureTestingModule  in app component spec ts  eliminates this error   describe  AppComponent        gt      beforeEach async      gt        TestBed configureTestingModule         declarations            AppComponent          HeroesComponent                 compileComponents              it  should create the app        gt        const fixture   TestBed createComponent AppComponent       const app   fixture debugElement componentInstance      expect app  toBeTruthy

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I am beginning Angular and in my case  the issue was that I hadn t saved the file after adding the  import  statement

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This convoluted framework is driving me nuts  Given that you defined the custom component in the the template of another component part of the SAME module  then you do not need to use exports in the module  e g  app module ts   You simply need to specify the declaration in the  NgModule directive of the aforementioned module      app module ts  import   JsonInputComponent   from    json-input json-input component     NgModule     declarations        AppComponent      JsonInputComponent              You do NOT need to import the JsonInputComponent  in this example  into AppComponent  in this example  to use the JsonInputComponent custom component in AppComponent template  You simply need to prefix the custom component with the module name of which both components have been defined  e g  app     lt form  formGroup   reactiveForm  gt     lt app-json-input formControlName  result  gt  lt  app-json-input gt   lt  form gt    Notice app-json-input not json-input   Demo here  https   github com lovefamilychildrenhappiness AngularCustomComponentValidation

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Route modules  did not saw this as an answer   First check  if you have declared- and exported the component inside its module  imported the module where you want to use it and named the component correctly inside the HTML   Otherwise  you might miss a module inside your routing module  When you have a routing module with a route that routes to a component from another module  it is important that you import that module within that route module  Otherwise the Angular CLI will show the error  component is not a known element   For example  1  Having the following project structure    ---core       ---sidebar              sidebar component ts              sidebar module ts     ---todos          todos-routing module ts          todos module ts             ---pages             edit-todo component ts             edit-todo module ts   2  Inside the todos-routing module ts you have a route to the edit todo component ts  without importing its module             path   edit-todo  todoId       component  EditTodoComponent         The route will just work fine  However when importing the sidebar module ts inside the edit-todo module ts you will get an error  app-sidebar is not a known element   Fix  Since you have added a route to the edit-todo component ts in step 2  you will have to add the edit-todo module ts as an import  after that the imported sidebar component will work

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A lot of answers comments mention components defined in other modules  or that you have to import declare the component  that you want to use in another component  in its their containing module  But in the simple case where you want to use component A from component B when both are defined in the same module  you have to declare both components in the containing module for B to see A  and not only A  I e  in my-module module ts import   AComponent   from  quot   A A component quot   import   BComponent   from  quot   B B component quot     NgModule     declarations        AComponent       This is the one that we naturally think of adding        BComponent          but forget this one and you get a  quot    AComponent                          is not a known element quot  error

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I got the same issue  and it was happening because of different feature module included this component by mistake  When removed it from the other feature  it worked

User · Answer

These are the 5 steps I perform when I got such an error   Are you sure the name is correct   also check the selector defined in the component  Declare the component in a module  If it is in another module  export the component  If it is in another module  import that module  Restart the cli   When the error eccors during unit testing  make sure your declared the component or imported the module in TestBed configureTestingModule  I also tried putting ContactBoxComponent in CustomersAddComponent and then in another one  from different module  but I got an error saying there are multiple declarations   You can t declare a component twice  You should declare and export your component in a new separate module  Next you should import this new module in every module you want to use your component  It is hard to tell when you should create new module and when you shouldn t  I usually create a new module for every component I reuse  When I have some components that I use almost everywhere I put them in a single module  When I have a component that I don t reuse I won t create a separate module until I need it somewhere else  Though it might be tempting to put all you components in a single module  this is bad for the performance   While developing  a module has to recompile every time changes are made  The bigger the module  more components  the more time it takes  Making a small change to big module takes more time than making a small change in a small module

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This question may seem old and odd  but when I was trying to load a module lazy loading  and getting the same error  I realized I was missing an exports clause for the component that shipped as a part of a larger module  This Angular io Link explains why  Components Services inside a module  remains private or protected  by default  To make them public  you have to export them  Expanding on  Robin Djikof s answer with  live-love code sample  this is what was technically missing in my case Angular 8    NgModule     declarations        SomeOtherComponent      ProductListComponent        imports        DependantModule        exports   ProductListComponent        lt - This line makes ProductListComponent available outside the module       while keeping SomeOtherComponent private to the module    export class SomeLargeModule

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Supposedly you have a component  product-list component ts  import   Component   from   angular core             Component           selector   pm-products             templateUrl     product-list component html                       export class ProductListComponent         pageTitle  string    product list          And you get this error   ERROR in src app app component ts 6 3 - error NG8001   pm-products  is not a known element   If  pm-products  is an Angular component  then verify that it is part of this module    app component ts  import   Component   from  quot  angular core quot    Component     selector   pm-root       pm-root    template       lt div gt  lt h1 gt   pageTitle   lt  h1 gt     lt pm-products gt  lt  pm-products gt     not a known element      lt  div gt         export class AppComponent     pageTitle  string    Acme Product Management      Make sure you import the component  app module ts   import   BrowserModule   from   angular platform-browser   import   NgModule   from   angular core    import   AppComponent   from    app component       -- gt  add this import  you can click on the light bulb in the squiggly line in VS Code  import   ProductListComponent   from    products product-list component      NgModule     declarations        AppComponent      ProductListComponent    -- gt  Add this line here         imports        BrowserModule        bootstrap   AppComponent        export class AppModule

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The problem in my case was missing component declaration in the module  but even after adding the declaration the error persisted   I had stop the server and rebuild the entire project in VS Code for the error to go away

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In my case  my app had multiple layers of modules  so the module I was trying to import had to be added into the module parent that actually used it pages module ts  instead of app module ts

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I was facing the same issue  In my case I have forgotten to declare Parent component in the app module ts As a example if you are using  lt app-datapicker gt  selector in ToDayComponent template  you should declare both ToDayComponent and DatepickerComponent in the app module ts

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I have the same issue width php storm version 2017 3  This fix it for me  intellij support forum  It was an error width  angular language service  https   www npmjs com package  angular language-service

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I know this is a long resolved problem  but in my case I had a different solution  It was actually a mistake I made that maybe you made as well and didn t fully notice  My mistake was that I accidentally placed a Module e g   MatChipsModule  MatAutoCompleteModule  on the declarations section  the section that is composed only by components e g   MainComponent  AboutComponent  This made all my other import unrecognizable

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I just had the exact same issue  Before trying some of the solutions posted here  you might want to check if the component really doesn t work  For me  the error was shown in my IDE  WebStorm   but it turned out that the code worked perfectly when i ran it in the browser   After I shut down the terminal  that was running ng serve  and restarted my IDE  the message stopped showing up

User · Answer

I had the same problem with Angular CLI  10 1 5 The code works fine  but the error was shown in the VScode v1 50 Resolved by killing the terminal  ng serve  and restarting VScode

[angular] Angular 2 'component' is not a known element

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