MemoryCache : LRU, type-safe, thread-safe memory cache class in Swift

by iOS Example

MemoryCache

Overview

MemoryCache is a memory cache class in swift.

  • The MemoryCache class incorporates LRU policies, which ensure that a cache doesn’t use too much of the system’s memory. If memory is needed by other applications, it removes some items from the cache, minimizing its memory footprint.
  • You can add, remove, and query items with expiration in the cache from different threads without having to lock the cache yourself. ( thread-safe )
  • Unlike the NSCache class, the cache guarantees a type by its key. ( type-safe )
let memoryCache = MemoryCache.default // or initialize

// Defining a string (or hash) key for a dog value.
let dogKey = StringKey<Dog>("dog")

// Setting a dog value in memoryCache.
memoryCache.set(dog, for: dogKey)

// Getting a cached dog value in memoryCache.
let cachedDog = try? memoryCache.value(for: dogKey)

// Removing a cached dog value in memoryCache.
memoryCache.remove(for: dogKey)

Usage

Basic

Defining keys

let dogKey = StringKey<Dog>("dog")

Adding a Cached Value

memoryCache.set(dog, for: dogKey)

Getting a Cached Value

let dog = try? memoryCache.value(for: dogKey)

Removing Cached Values

  • Removes the cache of the specified key.
memoryCache.remove(for: dogKey)
  • Removes the cache of the specified key if it expired.
memoryCache.removeIfExpired(for: dogKey)
  • Removes All.
memoryCache.removeAll()

Others

Properties

/// The maximum total cost that the memoryCache can hold before it starts evicting caches.
var totalCostLimit: Int

/// The maximum number of caches the memoryCache should hold.
var countLimit: Int

/// The total cost of values in the memoryCache.
var totalCost: Int

/// The number of values in the memoryCache.
var count: Int

/// A Boolean value indicating whether the memoryCache has no values.
var isEmpty: Bool

Implement delegate

import MemoryCache

class SomeClass: NSObject, MemoryCacheDelegate {

    let memoryCache: MemoryCache
    
    init() {
        memoryCache = MemoryCache.default
        
        ...
        
        super.init()

        memoryCache.delegate = self
    }
    
    func memoryCache(_ memoryCache: MemoryCache, willEvict cache: Any) {
        // Called when an cache is about to be evicted or removed from the memoryCache.
    }
}

Expiration date

You can specify expiration date for cache. The default expiration is .never.

/// The expiration date is `.never`.
memoryCache.set(dog, for: dogKey, expiration: .never)

/// The expiration date is `.seconds("""10s""")`.
memoryCache.set(dog, for: dogKey, expiration: .seconds(10))

/// The expiration date is `.date("""TOMORROW""")`.
memoryCache.set(dog, for: dogKey, expiration: .date(Date().addingTimeInterval(60 * 60 * 24)))

/// Remove the cache of the specified key if it expired.
memoryCache.removeIfExpired(for: dogKey)

Requirements

  • Swift 4.2 ~
  • Xcode 10.1 ~

Installation

CocoaPods

MemoryCache is available through CocoaPods. To install
it, simply add the following line to your Podfile:

pod 'MemoryCache'

Carthage

You can integrate via Carthage, too.
Add the following line to your Cartfile :

github "yysskk/MemoryCache"

and run carthage update

Author

Yusuke Morishita

License

MemoryCache is available under the MIT license. See the LICENSE file for more info.

GitHub

https://github.com/yysskk/MemoryCache