How to use NSCache

Question

Can someone give an example on how to use NSCache to cache a string? Or anyone has a link to a good explanation? I can\'t seem to find any..

Answer 1

Sample code for caching a string using NSCache in Swift:

var cache = NSCache()
cache.setObject("String for key 1", forKey: "Key1")
var result = cache.objectForKey("Key1") as String
println(result) // Prints "String for key 1"

To create a single app-wide instance of NSCache (a singleton), you can easily extend NSCache to add a sharedInstance property. Just put the following code in a file called something like NSCache+Singleton.swift:

import Foundation

extension NSCache {
    class var sharedInstance : NSCache {
        struct Static {
            static let instance : NSCache = NSCache()
        }
        return Static.instance
    }
}

You can then use the cache anywhere in the app:

NSCache.sharedInstance.setObject("String for key 2", forKey: "Key2")
var result2 = NSCache.sharedInstance.objectForKey("Key2") as String
println(result2) // Prints "String for key 2"