Prototype

Creates new objects by cloning an existing instance rather than constructing from scratch.

The Problem

Creating a new object is expensive or complex. You need a copy that starts as an exact replica of an existing one, with only a few differences.

How It Works

›Cloning is often faster than constructing from scratch
›Deep copy duplicates nested objects; shallow copy shares them — know the difference
›Clone preserves the internal state that may be hard to reconstruct externally
›The client does not need to know the concrete class of the object
›Useful for creating "template" objects with preset defaults

When to Use

✓Object construction is costly and a similar object already exists

✓Config or template objects shared as a starting point with minor variations

✓When you need to copy objects without depending on their concrete classes

✓Undo/redo — snapshot the state by cloning before modification

Real-World Examples

🍎

iOS

NSCopying / NSMutableCopying, UIImage copy, deep copy via NSKeyedArchiver

🤖

Android

Kotlin data class .copy(), Parcelable, Bundle.clone()

🌐

Web

structuredClone(), spread { ...obj }, Object.assign({}, obj)

Code Examples

Swift

final class Theme: NSCopying {
    var primaryColor: String
    var font: String
    var isDark: Bool

    init(color: String, font: String, dark: Bool) {
        primaryColor = color; self.font = font; isDark = dark
    }

    func copy(with zone: NSZone? = nil) -> Any {
        Theme(color: primaryColor, font: font, dark: isDark)
    }
}

let light = Theme(color: "#FF4D1C", font: "SF Pro", dark: false)
let dark   = light.copy() as! Theme
dark.isDark       = true
dark.primaryColor = "#FF6B47"

print(light.isDark)        // false — original unchanged
print(dark.isDark)         // true