Structs vs classes in iOS Swift - When to Use Which

The Big Idea

Discover why choosing structs or classes can save your app from hidden bugs and confusion!

The Scenario

Imagine you are building a contact list app. You try to keep track of each contact's details manually by copying and updating information everywhere in your code.

When you change a contact's phone number, you must find and update every place that holds that contact's data.

The Problem

This manual way is slow and confusing. You might forget to update some places, causing wrong or outdated info to show.

It's easy to make mistakes and hard to keep your app working well as it grows.

The Solution

Using structs and classes helps organize your data smartly. Structs make copies of data, so changes don't affect others unexpectedly.

Classes let you share data easily by reference, so updates happen everywhere automatically.

This clear difference helps you choose the right tool to keep your app's data safe and easy to manage.

Before vs After

✗ Before

var contact1 = ["name": "Alice", "phone": "123"]
var contact2 = contact1
contact2["phone"] = "456"  // manual copy, easy to mess up

✓ After

struct Contact {
  var name: String
  var phone: String
}
var contact1 = Contact(name: "Alice", phone: "123")
var contact2 = contact1
contact2.phone = "456"  // struct copy, safe and clear

What It Enables

It enables you to manage data safely and clearly, avoiding bugs and making your app easier to build and maintain.

Real Life Example

Think of a photo editing app: using classes for shared filters means changing a filter updates all photos using it, while using structs for individual photo settings keeps each photo's edits separate.

Key Takeaways

Manual data copying is error-prone and hard to maintain.

Structs create safe copies of data; classes share data by reference.

Choosing between structs and classes helps keep your app's data organized and bug-free.