BFAutoCache

A box value type for automatically caching the value to a specific backend(default is UserDefaults)

Motivation

Everytime you need to save & access a value which saved in UserDefaults, you'll probablly endup in such code fragment:

var isOn: Bool {
  set {
    UserDefaults.standard.set(newValue, forKey: "kIsOn")
  }
  get {
    return UserDefaults.standard.bool(forKey: "kIsOn")
  }
}

var userID: Int {
  set {
    UserDefaults.standard.set(newValue, forKey: "kUserID")
  }
  get {
    return UserDefaults.standard.integer(forKey: "kUserID")
  }
}

...

Things get much boring and annoying if you have a bunch of different values to handle. You have to repeatly write the same code for each value that need to read from/write to UserDefaults. Though you can wrapper a general method to make the setValue/getValue simpler, you still have to care about the "Key" name to make read/write consistent.

BFAutoCache makes such boring task much simpler and even a little bit funny!

Using BFAutoCache

To cache a value, a key is needed to save the value and retrieve it. So when defining a AutoCache value, a name is always required to bind the value. The value of the AutoValue instance is retrieved by accessing the value property.

Samples:

// This is equal to (by default Cachable implementation):
// UserDefaults.standard.set(1, forKey: "a")
// UserDefaults.standard.synchronize()
// print(UserDefaults.standard.int(forKey: "a"))

var i = AutoCache<Int>(name: "a")
i.value = 1
print(i.value)

Or you can use a initial value as the default value if there is no such key in Defaults
// This is equal to (by default Cachable implementation):
// UserDefaults.standard.regist(defaults: ["a": 1])
var i = AutoCache<Int>(name: "a", initial: 1)

var s = AutoCache<String>(name: "s")
s.value = "Snow"
print(s.value)

// This is equal to (by default Cachable implementation):
// UserDefaults.stand.set("Snow", forKey: "a")
// UserDefaults.synchronize()
// print(UserDefaults.standard.string(forKey: "a"))

There are also three operators which help maniplulate the AutoCache value much more easier and simple.

• To bind the key name with a default (if the key does not exist, the default value will be returned) value, use '~~':

var i = 1~~'i'
var s = "Ned"~~"LordOfNorth"

• To assign a value, use '<~'

i <~ 2
s <~ "Snow"

• To access the value, use '%%'

print(%%i)  // 2
print(%%s)  // Snow

• To clear a value in cache, assign a nil value to the AutoCache variable:

i <~ nil
s <~ nil

AutoCache value is particularly usaful when declaring multiple configuration properties in a struct or class. You can specify which properties need to be save/access from the backend cache or not.

For example:

struct Settings {
var delay: AutoCache<Int>      // need cache
var title: AutoCache<String>   // need cache
var brightness: Float          // not cache
}

var settings = Settings(delay: 11~~"Delay", name: "hello"~~"Title", brightness: 1.0)

BFAutoCache also supports Array & Dictionary of the basic value type that compatible with UserDefaults.

var cards: AutoCache<[Int]>
cards <~ [A, 2, J, K]

var books: AutoCache<[String: Float]>
books <~ ["Swift": 10.0, "Java": 8.0]

How to Install

Simply using Cocoapod:

pod 'BFAutoCache'

Enhance the BFAutoCache

Actually, any type that confirms to Cachable protocol can leverage the benefit of AutoCache box value. You can write you own cachable type extension to pass into AutoCache, for example, a sqlite wrapper or CoreData wrapper, or even a plist wrapper.