What is the syntax for declaring an object within an Angular component?

Question

What is the syntax for declaring an object within an Angular component?

Hello there, I'm fairly new to Angular and I've been encountering an issue with object declaration in one of my angular components.

import { Component } from '@angular/core';

@Component({
  selector: 'app-clases',
  templateUrl: './clases.component.html'

})
export class ClasesComponent
{

  alerta:string="alert-danger";

  constructor() {  }

  propiedades:Object = {
    danger: false
  }

}

Whenever I try to compile this code, I encounter an error:

***Compiled with problems:

Error: src/app/components/clases/clases.component.html:9:76 - error TS2339: Property 'danger' does not exist on type 'Object'.

9 <h3 [ngClass]="{'text-danger':propiedades.danger,'text-info':!propiedades.danger}"><
                                                                             ~~~~~~

  src/app/components/clases/clases.component.ts:5:16
    5   templateUrl: './clases.component.html'
                     ~~~~~~~~~~~~~~~~~~~~~~~~~
    Error occurs in the template of component ClasesComponent.

It appears that the 'danger' property in the class is not recognized causing this error to be thrown.

Any suggestions or help would be greatly appreciated!

angular typescript object web

Answer 1

Answer №1

To achieve the desired outcome, simply specify the type of variable propiedades as shown in the code snippet below.

import { Component } from '@angular/core';

@Component({
  selector: 'app-clases',
  templateUrl: './clases.component.html'
})
export class ClasesComponent {
  alerta = 'alert-danger';
 
  propiedades: {danger: boolean} = {
    danger: false
  };

  constructor() {}
}

Answer 2

To achieve the desired outcome, simply specify the type of variable propiedades as shown in the code snippet below.

import { Component } from '@angular/core';

@Component({
  selector: 'app-clases',
  templateUrl: './clases.component.html'
})
export class ClasesComponent {
  alerta = 'alert-danger';
 
  propiedades: {danger: boolean} = {
    danger: false
  };

  constructor() {}
}

Answer 3

Answer №2

With Typescript, you can rely on its ability to determine the object type automatically. This means you don't have to explicitly define it as shown below:

import { Component } from '@angular/core';

@Component({
  selector: 'app-clases',
  templateUrl: './clases.component.html'
})
export class ClasesComponent {
  alerta = 'alert-danger';
 
  propiedades = {
    danger: false
  };

  constructor() {}
}

If you were to specify the type as Object, and use this line in your template:

<h3 [ngClass]=" {'text-danger':propiedades.danger,'text-info':!propiedades.danger }">

The Angular/TypeScript compiler would expect the value to be an Object, which doesn't have a danger property.

Answer 4

With Typescript, you can rely on its ability to determine the object type automatically. This means you don't have to explicitly define it as shown below:

import { Component } from '@angular/core';

@Component({
  selector: 'app-clases',
  templateUrl: './clases.component.html'
})
export class ClasesComponent {
  alerta = 'alert-danger';
 
  propiedades = {
    danger: false
  };

  constructor() {}
}

If you were to specify the type as Object, and use this line in your template:

<h3 [ngClass]=" {'text-danger':propiedades.danger,'text-info':!propiedades.danger }">

The Angular/TypeScript compiler would expect the value to be an Object, which doesn't have a danger property.

Answer 5

Answer №3

In TypeScript, declaring Objects using interfaces can be done in 2 ways.

The first way is to use an interface when the exact keys are known:

import { Component } from '@angular/core';

interface Properties {
    danger: Boolean;    
}

@Component({
  selector: 'app-classes',
  templateUrl: './classes.component.html'

})
export class ClassesComponent
{

  alert:string="alert-danger";

  constructor() {  }

  properties: Properties = {
    danger: false
  }

}

The second way is to use an interface when the exact keys are not known:

import { Component } from '@angular/core';

interface Properties {
    [key: string]: Boolean;    
}

@Component({
  selector: 'app-classes',
  templateUrl: './classes.component.html'

})
export class ClassesComponent
{

  alert:string="alert-danger";

  constructor() {  }

  properties: Properties = {
    danger: false
  }

}

Answer 6

In TypeScript, declaring Objects using interfaces can be done in 2 ways.

The first way is to use an interface when the exact keys are known:

import { Component } from '@angular/core';

interface Properties {
    danger: Boolean;    
}

@Component({
  selector: 'app-classes',
  templateUrl: './classes.component.html'

})
export class ClassesComponent
{

  alert:string="alert-danger";

  constructor() {  }

  properties: Properties = {
    danger: false
  }

}

The second way is to use an interface when the exact keys are not known:

import { Component } from '@angular/core';

interface Properties {
    [key: string]: Boolean;    
}

@Component({
  selector: 'app-classes',
  templateUrl: './classes.component.html'

})
export class ClassesComponent
{

  alert:string="alert-danger";

  constructor() {  }

  properties: Properties = {
    danger: false
  }

}

What is the syntax for declaring an object within an Angular component?

Answer №1

Answer №2

Answer №3

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