Menene bambanci tsakanin struct da class a cikin Swift?

Question

IT Interview Practice · Accepted Answer

`struct` **value type** ne: ana kwafinsa a lokacin assignment, kuma kowane kwafi yana da 'yancin kansa. `class` kuma **reference type** ne: assignment yana raba instance guda ɗaya, kuma variables biyun suna nuni zuwa object guda. Wannan bambanci ɗaya yana jagorantar yawancin yanke shawara na zane a cikin Swift.

## Yadda yake aiki

```swift
struct PointS { var x: Int }
class  PointC { var x: Int; init(x: Int) { self.x = x } }

var a = PointS(x: 1)
var b = a          // COPY — b is a separate struct
b.x = 99
print(a.x, b.x)    // => 1 99  (a unaffected)

let c = PointC(x: 1)
let d = c          // SHARE — same instance
d.x = 99
print(c.x, d.x)    // => 99 99 (both changed)
```

## Fa'ida da hasara

| Fanni | struct (value) | class (reference) |
|--------|----------------|-------------------|
| Copy semantics | kwafi mai zaman kansa | reference da aka raba |
| Sauyi | yana bukatar `var` / `mutating` | ana iya sauya ta kowane reference |
| Identity | babu (kwatanta da value) | `===` identity |
| Inheritance | a'a | eh |
| Memory | yawanci stack, babu ARC | heap, ARC ke sarrafawa |

Structs kuma suna bukatar `mutating` don sauya stored properties a cikin method, saboda methods suna samun `self` marar sauyawa ta tsohuwa.

## Yaushe za a yi amfani da wanne

- **Fifita `struct`** — standard library na Swift (`Array`, `String`, `Int`) da SwiftUI `View`s duka value types ne. Suna da aminci don rabawa tsakanin threads kuma ba su da retain cycles.
- Yi amfani da `class` lokacin da kake bukatar **shared mutable state**, **identity**, **inheritance**, ko Objective-C interop (`NSObject`).

## Me ya sa yake da muhimmanci

Zaɓin value da reference yana yanke shawara ko sauyi a wuri ɗaya zai zuba zuwa wani wuri. Bugs inda "gyara abu ɗaya ya gyara duka" suna fitowa daga rabawar reference ba tsammani; dukkan model na SwiftUI yana ɗauka cewa akwai value-type views masu araha da sauƙin kwafi — don haka masu tambayoyi suna duba ko za ka kai ga `struct` da farko.

Fanni	struct (value)	class (reference)
Copy semantics	kwafi mai zaman kansa	reference da aka raba
Sauyi	yana bukatar `var` / `mutating`	ana iya sauya ta kowane reference
Identity	babu (kwatanta da value)	`===` identity
Inheritance	a'a	eh
Memory	yawanci stack, babu ARC	heap, ARC ke sarrafawa

Yadda yake aiki

Fa'ida da hasara

Yaushe za a yi amfani da wanne

Me ya sa yake da muhimmanci

Tambayoyi masu alaƙa