Get and set

Learn getter and setter methods.

What are getters and setters?

The get and set keywords define an accessor for a property. The getter runs when reading the property, the setter runs when assigning to it. This lets you keep a private backing field and control access. A getter takes no parameter, a setter takes one.

class Account {
  private _balance = 0;
  get balance() { return this._balance; }
  set balance(v: number) { this._balance = v; }
}

Validation with a getter

You can validate the assigned value by putting a condition inside the setter. If an invalid value is assigned, an error is thrown or the value is ignored. This preserves internal consistency. The getter usually just returns the private field.

class User {
  private _age = 0;
  get age() { return this._age; }
  set age(v: number) {
    if (v < 0) throw new Error("negative age");
    this._age = v;
  }
}

Exercise Sicaklik getter and setter

Define a Sicaklik class with a private _derece field starting at 0. get derece returns _derece. set derece(v: number) sets _derece to 0 if negative, otherwise to v. Add the lines const s = new Sicaklik(); s.derece = -5; console.log(s.derece);.

Show example solution

class Sicaklik {
  private _derece = 0;
  get derece() { return this._derece; }
  set derece(v: number) { this._derece = v < 0 ? 0 : v; }
}
const s = new Sicaklik();
s.derece = -5;
console.log(s.derece);

Test yourself

How many parameters does a setter method take?
- Two parameters
- Takes no parameters
- Any number of parameters
- Exactly one parameter
Show answer

Exactly one parameter — A setter takes exactly one parameter to receive the value being assigned; a getter takes none.

Getter keyword

class Kutu {
  private _icerik = 0;
  ____ icerik() { return this._icerik; }
}

Show answer

class Kutu {
  private _icerik = 0;
  get icerik() { return this._icerik; }
}

Accessor parts

get

Reads the value
set

Writes the value
özel alan

Backing field
doğrulama

Condition in setter

Next lesson: Summary - Advanced classes

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