Introduction

Turn any object into a discrete system where each state is a static data container.

How to install

The recommended way is to install using CocoaPods:

pod 'XCEStaticState', '~> 1.2'

How it works

This library allows to turn any object into discrete system by defining a number of distinct states for any object and then set any of these states as current state of the object. Same state can be re-set multiple times without any limitations.

How to use

A typical use case for this library is to store different set of internal data (and provide access to diffrent functionality, incapsulated in state types) at different points of time as well as indicating current internal state of a given object. Any object can only be in one particular state at any point of time, or current state might be undefined.

State

Let’s say we have class MyView…

class MyView
{
    // class definition goes here...
}

… and it can only be in 3 different states: Normal, Disabled or Highlighted. Every state must be declared as an instantiatable type that conforms to State protocol. For the sake of simplicity, lets assume that Normal contains no extra data, Disabled holds opacity amount and Highlighted contains color value which is just a number that represents a code for color.

extension MyView
{
    struct Normal: State
    {
        typealias Owner = MyView
    }
    
    struct Disabled: State
    {
        typealias Owner = MyView
        
        var opacity: Float
    }
    
    struct Highlighted: State
    {
        typealias Owner = MyView
    
        let color: Int
    }
}

Stateful

Any object for which we want to track its current state should be of type that conforms to Stateful protocol. That protocol only requires to declare one var property state where current state supposed to be stored:

var state: Any?

Let’s update the initial class declaration:

class MyView: Stateful
{
    var state: Any?
}

We can set current state as follows:

let aView = MyView()

aView.state = MyView.Disabled(opacity: 0.3)
aView.state = MyView.Normal()
aView.state = MyView.Highlighted(color: 1)
// 'aView.state' is now 'Highlighted' with 'color' equal to '1'

Note, that in the beginning the state property is nil until you set a value explicitly; after this it holds assigned value indefinitely until you assign another value, nil or the object itself is deallocated.

var aView = MyView()

aView.state = MyView.Normal()
// 'aView.state' is now 'Normal'

aView = MyView() // released previosly created object of type 'MyView'
// 'aView.state' is now 'nil'

aView.state = MyView.Disabled(opacity: 0.3)
// 'aView.state' is now 'Disabled' with 'opacity' equal to '0.3'

Helper functions

Moreover, Stateful protocol provides provides several functions that allow to dial with state solely via functions.

let aView = MyView()

aView.set(MyView.Normal())
// current state of 'aView' object is now 'Normal'

aView.set(MyView.Disabled(opacity: 0.3))
// current state of 'aView' object is now 'Disabled' with 'opacity' equal to '0.3'

try? aView.update(MyView.Disabled.self){ $0.opacity += 0.2 }
// current state of 'aView' object is now 'Disabled' with 'opacity' equal to '0.5'

if
    let d = try? aView.currentState() as? MyView.Disabled
{
    // 'd' now holds an instace of 'Disabled' type with 'opacity' equal to '0.5'
}

aView.resetCurrentState()
// current state of 'aView' object is now 'nil'