Learning Sequence and Generators

CustomCollection.swift

struct Stack<T> {

    private var store = [T]()

    mutating func push(anObject: T) {
        store.append(anObject)
    }

    mutating func pop() -> T? {
        let lastItem = store.last
        store = Array(store.dropLast())
        return lastItem
    }
}

/// Using stack to create stack generator
/// Thanks Psy
struct StackGenerator<T>: GeneratorType {
    var stack: Stack<T>
    mutating func next() -> T? {
        return stack.pop()
    }
}

extension Stack: SequenceType {
    func generate() -> StackGenerator<T> {
        return StackGenerator<T>(stack: self)
    }
}

struct ArrayGenerator<T>: GeneratorType {

    var items: [T]

    mutating func next() -> T? {
        if items.isEmpty  { return .None }
        let element = items.last!
        items = Array(items[0..<items.count-1])
        return element
    }
}

///Using ArrayGenerator
//extension Stack: SequenceType {
//    func generate() -> ArrayGenerator<T> {
//        return ArrayGenerator<T>(items: store)
//    }
//}

///Easy Way
//extension Stack: SequenceType {
//    func generate() -> IndexingGenerator<[T]> {
//        return store.reverse().generate()
//    }
//}

var fruitStore = Stack<String>()
fruitStore.push("apple")
fruitStore.push("banana")
fruitStore.pop()
fruitStore.push("banana2")
fruitStore.push("banana3")

for fruit in fruitStore {
    print("\(fruit)")
}

print("")
//=========================================================================================================//

struct StringStack {

    private var stackStore = [String]()

    mutating func push(someString: String) {
        stackStore.append(someString)
    }

    mutating func pop() -> String? {
        let lastItem = stackStore.last
        stackStore = Array(stackStore.dropLast())
        return lastItem
    }
}

var fruitStack = StringStack()

fruitStack.push("apple")
fruitStack.push("banana")
fruitStack.push("orange")
fruitStack.push("papaya")
fruitStack.pop()

//for fruit in fruitStack.stackStore {
//    print("\(fruit)")
//}

struct StringStackGenerator: GeneratorType {

    var items: [String]

    mutating func next() -> String? {
        if items.isEmpty  { return .None }
        let element = items.last!
        items = Array(items[0..<items.count-1])
        return element
    }
}

extension StringStack: SequenceType {
    func generate() -> StringStackGenerator {
        return StringStackGenerator(items: stackStore)
    }
}

//Easy way
//extension StringStack: SequenceType {
//    func generate() -> IndexingGenerator<[String]> {
//        return stackStore.reverse().generate()
//    }
//}

for fruit in fruitStack {
    print("\(fruit)")
}

struct Stack<T> {    
    private var store: [T] = []
    mutating func push(anObject: T) { store.append(anObject) }
    mutating func pop() -> T? {return store.isEmpty ? nil : store.removeLast() }
}

struct ArrayGenerator<T>: GeneratorType {
    var items: [T]
    mutating func next() -> T? {
        return items.isEmpty ? .None : items.removeLast()
    }
}

struct Stack<T> {
    private var store: [T] = []
    mutating func push(anObject: T) { store.append(anObject) }
    mutating func pop() -> T? { return store.isEmpty ? nil : store.removeLast() }
}

/// Using Stack to create stack generator
/// Thanks Psy
struct StackGenerator<T>: GeneratorType {
    var stack: Stack<T>
    mutating func next() -> T? { return stack.pop() }
}

extension Stack: SequenceType {
    func generate() -> StackGenerator<T> { return StackGenerator<T>(stack: self) }
}

var fruitStore = Stack<String>()
fruitStore.push("apple")
fruitStore.push("banana")
fruitStore.pop()
fruitStore.push("banana2")
fruitStore.push("banana3")

for fruit in fruitStore {
    print("\(fruit)")
}

❤️ thanks erica