Encapsulation nima ne?

Question

Accepted Answer

**Encapsulation** yana nufin ɗammawa da data da hanyoyin da suke aiki akan shi a cikin sashe gida (class) da **ɓoye internal state** a bayan gida ta hanyar shawo da zaune. Masu kira suna hulɗa ta hanyar hanyoyin aiki, ba ta hanyar tunkarar filayen zahiri.

## Me yasa a ɓoye state

Idan kowa zai iya canja filin kai tsaye, ba za ka iya gida kowa ne object yana da kyau. Encapsulation yana ba da damar class ne **shigar da niyyarsa.

```java
public class Account {
    private double balance;             // hidden: no direct access

public void withdraw(double amount) {
        if (amount <= 0)                // guard the invariant
            throw new IllegalArgumentException("amount must be positive");
        if (amount > balance)
            throw new IllegalStateException("insufficient funds");
        balance -= amount;              // only valid changes get through
    }

public double getBalance() { return balance; }
}
```

```java
// Without encapsulation, this would be possible and disastrous:
account.balance = -5000;   // bypasses every rule
```

Domin `balance` ya zama mai sirri, *kawai* hanya don canja ta wuce ta `withdraw`, wanda ke garding dokokin.

## Wahala

Encapsulation ba "ƙarawa getter/setter ga kowane filin" ba ne. Bayyanawa setter ga komai shi kamar filayen jari ko da wajal. Bayyana *hali*, ba raw state ba.

## Me yasa yake muhimmi

Encapsulation tana kiyaye invariants a gida, don bug a kula da balance zai iya zauna a cikin `Account" ne kawai, ba ta yaɗuwa a gida.

Hakanan yana ba da damar ka canja wakilcin ciki a gida (adana cents a matsayin integer, ƙara logging) ba tare da atsowa masu kira ba, saboda suna dogara ne akan gida.