How do I declare a model class in my Angular 2 component using TypeScript

Question

I am new to Angular 2 and TypeScript and I m trying to follow best practices   Instead of using a simple JavaScript model        I m attempting to create a TypeScript class   However  Angular 2 doesn t seem to like it   My code is   import   Component  Input   from   angular core     Component       selector   testWidget       template    lt div gt This is a test and   model param1   is my param  lt  div gt       export class testWidget       constructor private model  Model        class Model       param1  string      and I m using it as   import   testWidget  from  lib testWidget     Component       selector   myComponent       template    lt testWidget gt  lt  testWidget gt        directives   testWidget       I m getting an error from Angular      EXCEPTION  Can t resolve all parameters for testWidget         So I thought  Model isn t defined yet    I ll move it to the top   Except now I get the exception      ORIGINAL EXCEPTION  No provider for Model    How do I accomplish this    Edit  Thanks to all for the answer   It led me to the right path   In order to inject this into the constructor  I need to add it to the providers on the component    This appears to work   import   Component  Input   from   angular core    class Model       param1  string      Component       selector   testWidget       template    lt div gt This is a test and   model param1   is my param  lt  div gt        providers   Model      export class testWidget       constructor private model  Model

User · Answer

In your case you are having model on same page, but you have it declared after your Component class, so that's you need to use forwardRef to refer to Class. Don't prefer to do this, always have model object in separate file.

export class testWidget {
    constructor(@Inject(forwardRef(() => Model)) private service: Model) {}
}

Additionally you have to change you view interpolation to refer to correct object

{{model?.param1}}

Better thing you should do is, you can have your Model Class define in different file & then import it as an when you require it by doing. Also have export before you class name, so that you can import it.

import { Model } from './model';

User · Answer

create model ts in your component directory as below   export module DataModel          export interface DataObjectName            propertyName  type                   export interface DataObjectAnother            propertyName  type                    then in your component import above as  import  DataModel  from    model    export class YourComponent      public DataObject  DataModel DataObjectName      your DataObject should have all the properties from DataObjectName

User · Answer

You can use the angular-cli as the comments in  brendon s answer suggest   You might also want to try   ng g class modelsDirectoy modelName --type model     will create  src app modelsDirectoy   -- modelName model ts   --               Bear in mind   ng g class     ng g c However  you can use ng g cl as shortcut depending on your angular-cli version

User · Answer

my code is       import   Component   from   angular core    class model     username   string    password   string      Component     selector   app-root     templateUrl     app component html     styleUrls      app component css         export class AppComponent     username   string   password   string    usermodel   new model       login      if this usermodel username     admin        alert  hi       else      alert  bye        this usermodel username                       and the html goes like this     lt div class  login  gt    Usernmae    lt input type  text    ngModel    usermodel username   gt    Password    lt input type  text    ngModel    usermodel password   gt     lt input type  button  value  Click Me   click   login      gt   lt  div gt

User · Answer

export class Car     id  number    make  string    model  string    color  string    year  Date     constructor car                    this id   car id          this make   car make                this model   car model                this color   car color                this year   new Date car year  getYear                    The    can become super useful for very complex data objects to default data that doesn t exist        In your component ts or service ts file you can deserialize response data into the model      Import the car model import   Car   from    car model ts       If single object car   new Car someObject       If array of cars cars   someDataToDeserialize map c   gt  new Car c

User · Answer

I d try this   Split your Model into a separate file called model ts   export class Model       param1  string      Import it into your component  This will give you the added benefit of being able to use it in other components   Import   Model   from    model     Initialize in the component   export class testWidget      public model  Model     constructor           this model   new Model           this model param1    your string value here            Access it appropriately in the html    Component         selector   testWidget         template    lt div gt This is a test and   model param1   is my param  lt  div gt        I want to add to the answer a comment made by  PatMigliaccio because it s important to adapt to the latest tools and technologies      If you are using angular-cli you can call ng g class model and it will generate it for you  model being replaced with whatever naming you desire

User · Answer

I realize this is a somewhat older question  but I just wanted to point out that you ve add the model variable to your test widget class incorrectly  If you need a Model variable  you shouldn t be trying to pass it in through the component constructor  You are only intended to pass services or other types of injectables that way  If you are instantiating your test widget inside of another component and need to pass a model object as  I would recommend using the angular core OnInit and Input Output design patterns   As an example  your code should really look something like this   import   Component  Input  OnInit   from   angular core   import   YourModelLoadingService   from     yourModuleRootFolderPath index   class Model       param1  string      Component       selector   testWidget       template    lt div gt This is a test and   model param1   is my param  lt  div gt        providers    YourModelLoadingService       export class testWidget implements OnInit        Input   model  Model    Use this if you want the parent component instantiating this           one to be able to directly set the model s value     private  model  Model    Use this if you only want the model to be private within           the component along with a service to load the model s value     constructor          private  yourModelLoadingService  YourModelLoadingService   This service should           usually be provided at the module level  not the component level               ngOnInit             this load               private load               add some code to make your component read only            possibly add a busy spinner on top of your view           This is to avoid bugs as well as communicate to the user what s           actually going on            If using the Input model so the parent scope can set the contents of model            add code an event call back for when model gets set via the parent           On event  now that loading is done  disable read only mode and your spinner           if you added one            If using the service to set the contents of model  add code that calls your           service s functions that return the value of model           After setting the value of model  disable read only mode and your spinner           if you added one  Depending on if you leverage Observables  or other methods           this may also be done in a callback           A class which is essentially just a struct model should not be injected  because it means you can only have a single shared instanced of that class within the scope it was provided  In this case  that means a single instance of Model is created by the dependency injector every time testWidget is instantiated  If it were provided at the module level  you would only have a single instance shared among all components and services within that module   Instead  you should be following standard Object Oriented practices and creating a private model variable as part of the class  and if you need to pass information into that model when you instantiate the instance  that should be handled by a service  injectable  provided by the parent module  This is how both dependency injection and communication is intended to be performed in angular   Also  as some of the other mentioned  you should be declaring your model classes in a separate file and importing the class   I would strongly recommend going back to the angular documentation reference and reviewing the basics pages on the various annotations and class types  https   angular io guide architecture  You should pay particular attention to the sections on Modules  Components and Services Dependency Injection as these are essential to understanding how to use Angular on an architectural level  Angular is a very architecture heavy language because it is so high level  Separation of concerns  dependency injection factories and javascript versioning for browser comparability are mainly handled for you  but you have to use their application architecture correctly or you ll find things don t work as you expect

User · Answer

The problem lies that you haven t added Model to either the bootstrap  which will make it a singleton   or to the providers array of your component definition    Component       selector   testWidget       template    lt div gt This is a test and   param1   is my param  lt  div gt        providers            Model           export class testWidget       constructor private model  Model         And yes  you should define Model above the Component  But better would be to put it in his own file   But if you want it to be just a class from which you can create multiple instances  you better just use new    Component       selector   testWidget       template    lt div gt This is a test and   param1   is my param  lt  div gt       export class testWidget        private model  Model   new Model         constructor

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