Let's talk about creating a variable for a car:
export class ICar {
wheels: number;
color: string;
type: string;
}
So, which way is better to create the variable?
Option one:
const car = {
wheels: 4,
color: 'red',
type: 'truck'
} as ICar;
Or maybe option two:
var car = new ICar();
car.wheels = 4;
car.color = 'red';
car.type = 'truck';
If ICar is defined as a class, then the initial example provided is indeed incorrect.
To elaborate on the example given, let's consider the following:
export class ICar {
wheels: number;
color: string;
type: string;
constructor() {
this.wheels = 2;
this.color = 'blue';
this.type = 'motorcycle'
}
drive() {
console.log('Driving!')
}
}
The proper way to create an instance of a class is by using the new keyword.
// Correct approach
var car1 = new ICar();
car1.wheels = 4;
car1.color = 'red';
car1.type = 'truck';
car1.drive() // Executed successfully
It is important to note the significance of the last line car1.drive(), which only works because the class was instantiated.
On the other hand, if we attempt a similar process with a typecast:
// Not recommended
const car2 = {
wheels: 4,
color: 'red',
type: 'truck'
} as ICar;
car2.drive() // Error at runtime
Subsequently, invoking car2.drive() results in a runtime error since the method does not exist within that context. This issue arises because the use of as ICar does not actually transform the object into an instance of ICar; it solely informs Typescript to treat the value differently without altering its nature.
Hence, employing as in such scenarios introduces bugs that could have been caught by Typescript.
By experimenting with it in the TypeScript Playground, you'll discover that your code doesn't compile as expected.
An interface might be more suitable than a class. An interface defines the structure an object should have, while a class includes contructor(), methods, and unnecessary elements. Here's how I would approach your scenario:
// Define an interface to describe the characteristics of a car
export interface ICar {
wheels: number;
color: string;
type: string;
}
// Create a variable following the ICar interface,
// and assign it a valid object
const car1: ICar = {
wheels: 4,
color: 'red',
type: 'truck'
};
It is advisable to opt for the second option
var vehicle = {};
vehicle.wheels = 4;
vehicle.color = 'red';
vehicle.type = 'truck';
The initial object is defined using const, making it immutable. Therefore, selecting the first choice would be more appropriate.
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