B/O - State

• Category: behavioral
• Type: object
• Motivation: change the behavior of a class when the state changes
  • implements a state machine in an object-oriented way
  • invoke the method in state object

do {
    let editor = Editor()
    editor.type("hello WORLD")

    editor.state = Upppercase()
    editor.type("hello world")

    editor.state = Lowercase()
    editor.type("hello world")
}

class Editor
{
    var state: Writing = Default()

    func type(_ words: String)
    {
        state.write(words)
    }
}

protocol Writing
{
    func write(_ words: String)
}

class Default: Writing
{
    func write(_ words: String)
    {
        print(words)
    }
}

class Upppercase: Writing
{
    func write(_ words: String)
    {
        print(words.uppercased())
    }
}

class Lowercase: Writing
{
    func write(_ words: String)
    {
        print(words.lowercased())
    }
}