'Cannot approach Typescript enum within HTML

I made an enum with Typescript to use in MyService.service.ts MyComponent.component.ts and MyComponent.component.html. 

export enum ConnectionResult {
    Success,
    Failed     
}

I can easily get and compare a defined enum variable from MyService.service.ts:

this.result = this.myService.getConnectionResult();

switch(this.result)  
{
    case ConnectionResult.Failed:
         doSomething();
         break;
    case ConnectionResult.Success:
         doSomething();
         break;
}

I also wanted to use the enum for a comparison within my HTML using the *ngIf statement:

<div *ngIf="result == ConnectionResult.Success; else failed">
            <img src="../../assets/connection-success.png" height="300px" class="image-sign-style" />
</div>
<ng-template #failed>
       <img src="../../assets/connection-failed.png" height="300px" class="image-sign-style" />
</ng-template>

The code compiles but the browser gives me an error:

Cannot read property of undefined

enter image description here

With the following html indication error line:

enter image description here

Does anyone know why the enum cannot be approached like this?

htmlangulartypescriptenums


Solution 1:[1]

The scope of the template is limited to the component instance members. If you want to refer to something it needs to be available there

class MyComponent {
  public get connectionResult(): typeof ConnectionResult {
    return ConnectionResult; 
  }
}

In the HTML you can now use

*ngIf="connectionResult.Success"

See also Angular2 access global variables from HTML template

Solution 2:[2]

You will have to write it in the following way in .ts file.

enum Tenure { day, week, all }

export class AppComponent {
    tenure = Tenure.day
    TenureType = Tenure
}

And now in html you can use this like

*ngIf = "tenure == TenureType.day ? selectedStyle : unSelectedStyle"

I hope it is more clear now. :)

Solution 3:[3]

You can just add the enum to your component as property and use the same name of the enum (Quarters) in your templates:

enum Quarters{ Q1, Q2, Q3, Q4}

export class AppComponent {
   quarter = Quarters.Q1
   Quarters = Quarters //here you are creating a variable/alias to the enum
}

In your template

<div *ngIf="quarter == Quarters.Q1">I=am only visible for Q1</div>

The reason why this works is that the new porperty is basically of this type:

TileType: typeof TileType

Solution 4:[4]

import MyEnum from enums;

.... Declarate var ....

public myEnum = MyEnum;

and in html use:

<div *ngIf="xxx === myEnum.DATA"> ... </div>

Solution 5:[5]

You can bind as text if enum defined as below (those values won't enforce a json string value coming from API)

  export enum SomeEnum {
      Failure = "Failure",
      Success = "Success",
  }

In .ts file

public status: SomeEnum;

In .html

<div *ngIf="status == 'Success'">

Another way, tested in Angular 8+ is to have enums with numbers

  export enum SomeEnum {
      Failure = 0,
      Success = 1,
  }

In .ts file

public status: SomeEnum;

In .html

<div *ngIf="status == 1">

Solution 6:[6]

In your Service

export enum ConnectionResult {
    Success,
    Failed     
}

Assign the enum to a varaible in TypeScript File

ConnectionResult = ConnectionResult;

Then read your Enum from HTML as bellow

*ngIf="result == ConnectionResult.Success"

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Hypenate
Solution 2
Solution 3 Mauricio Gracia Gutierrez
Solution 4 João Marcos Santos Teixeira
Solution 5 Jöcker
Solution 6 Dimuth

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