TypeScript - Classes - public methods and access modifiers

Now the question arises, If i have declared private and protected properties in a class. How can we modify them? The answer is, we modify them using public methods of the class.

In the below example, we have a class City in which, we have 2 private properties:

• type
• elevation

Okay, elevation here is protected. But, remember, protected property is a private property. It has an additional feature that it can get inherited by a child class.

class City {

public name:string;

private type: string;

protected elevation: number;

constructor(name:string) {

this.name = name;

this.type = "city";

this.elevation = 505;

}

setElevation(elevation:number){

this.elevation = elevation;

console.log("new elevation = "+this.elevation);

}

getElevation(){

console.log(this.elevation);

}

setType(type:string){

this.type = type;

console.log("new type = "+this.type);

}

printType(){

console.log(this.type);

}

}

const city = new City("Hyderabad");

console.log(city);

city.getElevation();

city.setElevation(506);

city.printType();

city.setType("Metro");

city.printType();

To access these two private properties, we have created 4 public methods.

• 2 methods for setting value
• 2 methods for getting the value of these properties

The public methods created here are:

• getElevation
• setElevation
• printType
• setType

The set methods accept one argument here - which modifies the corresponding private properties.
The get methods enable us to retrieve the values contained in the private properties.

Let us compile the class:

$ tsc
$

Console Output:

City {name: "Hyderabad", type: "city", elevation: 505}
city-App.ts:104 505
city-App.ts:100 new elevation = 506
city-App.ts:113 city
city-App.ts:109 new type = Metro
city-App.ts:113 Metro

We can observe here - how the properties are affected using the set methods. Also, the output from the get methods are also visible in the Console.