The Flyweight pattern

The Flyweight pattern is used to optimize memory usage or computational resources by sharing common parts of objects. It's especially useful in scenarios where a large number of similar objects need to be created, and the overhead of creating individual objects with identical intrinsic states is too high.

Imagine you're building a drawing app where you need to render thousands of small circles with different colors on the screen. Without the Flyweight pattern, you would create a separate circle object for each with its color, which could consume a lot of memory. Here's how you can use the Flyweight pattern to optimize this:

1. Create a Flyweight Protocol: Define a protocol, let's call it CircleFlyweight, that declares the common properties and methods all circles will have. In this case, it might have a method to draw the circle.

protocol CircleFlyweight {
    func draw(at position: CGPoint)
}        

1. Create a Concrete Flyweight Class: Implement a concrete class that conforms to the CircleFlyweight protocol. This class should represent the shared properties of a circle, like its color.

class SharedCircle: CircleFlyweight {

    private let color: UIColor

    init(color: UIColor) {
        self.color = color
    }

    func draw(at position: CGPoint) {
        // Draw the circle with the shared color
    }
}        

1. Create a Flyweight Factory: Create a factory class that manages the shared flyweight objects. It keeps track of existing flyweights and returns the appropriate one when requested. This factory ensures that you're not creating duplicate objects for the same properties.

class CircleFlyweightFactory {
    private var circleFlyweights: [UIColor: CircleFlyweight] = [:]

    func getCircle(color: UIColor) -> CircleFlyweight {
        if let existingCircle = circleFlyweights[color] {
            return existingCircle
        } else {
            let newCircle = SharedCircle(color: color)
            circleFlyweights[color] = newCircle
            return newCircle
        }
    }
}        

Some of the realtime Usecases: --

1. Text Editor or Word Processing App: In a text editor app, you can use the Flyweight pattern to represent character or font attributes. Common fonts, styles, and character attributes can be shared among multiple characters, reducing memory overhead.
2. Drawing and Painting Apps: Drawing and painting apps often involve the creation of many similar shapes (e.g., lines, circles, polygons) with various colors and sizes. The Flyweight pattern can help share common properties like colors and line styles among these shapes.
3. Maps and Location-Based Apps: When displaying a map with a large number of markers, you can use Flyweight to optimize memory usage by sharing common marker icons, colors, or other visual properties.
4. Gaming Apps: Games often involve rendering numerous game objects (e.g., particles, bullets, enemies) with shared characteristics. Applying the Flyweight pattern can help manage and optimize the memory usage of these objects.
5. Inventory Management Apps: In apps that deal with inventory management, products, or items, you can use Flyweight to represent shared properties like product descriptions, categories, or images to reduce the memory footprint.
6. Music Streaming Apps: In music streaming apps, metadata for songs (e.g., artist names, album covers) can be shared among multiple instances of the same song, improving memory efficiency.
7. Calendar and Scheduling Apps: Calendar events often share common properties like event types, locations, or attendees. Using Flyweight, you can reduce the memory used for these properties when managing a large number of events.
8. Weather Apps: Weather data often involves shared attributes such as temperature units, weather icons, or location details. Flyweight can help minimize memory usage when displaying weather information for multiple locations.
9. Chat and Messaging Apps: In chat applications, you can use Flyweight to optimize the storage and memory usage of user avatars, emojis, or stickers that are shared among multiple conversations.
10. E-commerce Apps: In e-commerce apps, product details such as images, descriptions, and prices can be shared among multiple instances of the same product, helping reduce memory overhead.

In these scenarios, the Flyweight pattern helps maintain application performance and responsiveness while efficiently managing memory resources, especially when dealing with a large number of objects with shared characteristics.