📦 A simple, lightweight caching library for Swift.

What's New



What's Changed


Breaking Change

  • Update PersistableCache to use mappings by @0xLeif in #13

Full Changelog: 2.0.0...2.1.0


A simple, lightweight caching library for Swift.

What is Cache?

Cache is a Swift library for caching arbitrary data types in memory. It provides a simple and intuitive API for storing, retrieving, and removing objects from the cache.


  • Generic value type
  • Supports JSON serialization and deserialization
  • Flexible caching, allowing for multiple Cache objects with different configurations
  • Thread-safe implementation
  • Property Wrappers


Swift Package Manager (SPM)

Add the following line to your Package.swift file in the dependencies array:

dependencies: [
    .package(url: "", from: "2.0.0")


Basic Usage

First, import the Cache module:

import Cache

Create a cache instance with a generic key-value pair:

let cache = Cache<CacheKey, String>()

Add values to the cache using a key-value syntax:

cache[.text] = "Hello, World!"

Retrieve values using the same key-value syntax:

let cachedValue = cache[.text]

Multiple Cache Objects

You can create multiple Cache objects by specifying a different type of key-value pair:

let cache1 = Cache<CacheKey, String>()
let imageCache = Cache<URL, UIImage>()

Using JSON

You can use JSON to parse and serialize JSON data in the cache:

let json: JSON<CacheKey> = JSON(data: jsonData)

Removing Values

You can remove values from the cache using the remove method:


You can also just set the value to nil using the subscripts

cache[.text] = nil


The ExpiringCache class is a cache that retains and returns objects for a specific duration set by the ExpirationDuration enumeration. Objects stored in the cache are automatically removed when their expiration duration has passed.


// Create an instance of the cache with a duration of 5 minutes
let cache = ExpiringCache<String, Int>(duration: .minutes(5))

// Store a value in the cache with a key
cache["Answer"] = 42

// Retrieve a value from the cache using its key
if let answer = cache["Answer"] {
    print("The answer is \(answer)")

Expiration Duration

The expiration duration of the cache can be set with the ExpirationDuration enumeration, which has three cases: seconds, minutes, and hours. Each case takes a single UInt argument to represent the duration of that time unit.


The PersistableCache class is a cache that stores its contents persistently on disk using a JSON file. Use it to create a cache that persists its contents between application launches. The cache contents are automatically loaded from disk when initialized, and can be saved manually whenever required.

To use PersistableCache, make sure that the specified key type conforms to both RawRepresentable and Hashable protocols. The RawValue of Key must be a String type.

Here's an example of creating a cache, setting a value, and saving it to disk:

enum Key: String {
    case pi

let cache = PersistableCache<Key, Double, Double>()

cache[.pi] = Double.pi

do {
} catch {
    print("Failed to save cache: \(error)")

You can also load a previously saved cache from disk:

let cache = PersistableCache<Key, Double, Double>()

let pi = cache[.pi] // pi == Double.pi

Remember that the save() function may throw errors if the encoder fails to serialize the cache to JSON or the disk write operation fails. Make sure to handle the errors appropriately.

Advanced Usage

You can use Cache as an observed object:

struct ExampleView: View {
    enum Key {
        case title

    @ObservedObject var cache = Cache<Key, String>()

    var body: some View {
            "Cache Title",
            text: $cache[.title, default: ""]

Cacheable Functions

Cacheable protocol defines the following functions which can be used to work with the Cache or JSON.


allValues property returns a dictionary containing all the key-value pairs stored in the cache.

var allValues: [Key: Value] { get }


The init function initializes the cache instance with an optional dictionary of key-value pairs.

init(initialValues: [Key: Value])


The get function retrieves the value of the specified key and casts it to a given output type (if possible).

func get<Output>(_ key: Key, as: Output.Type) -> Output?

Alternatively, calling get with only the key returns the value casted to the default Value type.

func get(_ key: Key) -> Value?


The resolve function retrieves the value of the specified key and casts it to a given output type, but throws an error if the specified key is missing or if the value cannot be casted to the given output type.

func resolve<Output>(_ key: Key, as: Output.Type) throws -> Output

Alternatively, calling resolve with only the key casts the value to the default Value type.

func resolve(_ key: Key) throws -> Value


The set method sets the specified value for the specified key in the cache.

func set(value: Value, forKey key: Key)


The remove method removes the value of the specified key from the cache.

func remove(_ key: Key)


The contains method returns a Boolean indicating whether the cache contains the specified key.

func contains(_ key: Key) -> Bool


The require function ensures that the cache contains the specified key or keys, or else it throws an error.

func require(_ key: Key) throws -> Self
func require(keys: Set<Key>) throws -> Self


The values function returns a dictionary containing only the key-value pairs where the value is of the specified output type.

func values<Output>(ofType: Output.Type) -> [Key: Output]

The default value for ofType parameter is Value.


If you have improvements or issues, feel free to open an issue or pull request!


Cache is released under the MIT License. See LICENSE for details.


  • Swift Tools 5.6.0
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Last updated: Wed May 22 2024 14:27:39 GMT-0900 (Hawaii-Aleutian Daylight Time)