//
//  ViewController.swift
//  calculator
//
//  Created by 郭百度 on 2017/9/23.
//  Copyright ? 2017年 Luke. All rights reserved.
//

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var display: UILabel!
    var userIsInTheMiddleOfTyping = false
    var lessOnePoint = true
    @IBAction func touchDigit(_ sender: UIButton) {
        let digit = sender.currentTitle!
        //課后修正計算器bug添加，當(dāng)輸入為"."時判斷，屏幕上數(shù)字是否已有小數(shù)點，是的話不執(zhí)行
        let point: Character = "."
        if digit == String(point) && display.text!.contains(".") {
                lessOnePoint = false
        }
        if lessOnePoint {
            if userIsInTheMiddleOfTyping {
                let textCurrentlyInDisplay = display.text!
                display.text = textCurrentlyInDisplay + digit
                print("I'm \(digit) b")
            } else {
                display.text = digit
                userIsInTheMiddleOfTyping = true
                print("I'm \(digit) c")
            }
        }
        lessOnePoint = true
    }
    
    var displayVaule: Double {
        get {
            return Double(display.text!)!
        }
        set {
            display.text = String(newValue)
        }
    }

    private var  brain = CalculatorBrain()
    
    @IBAction func performOperation(_ sender: UIButton) {
        //執(zhí)行運算按鈕中，如果用戶正在鍵入中,那么將display值提交到brain的蓄存器中，用于實現(xiàn)當(dāng)用戶點擊開根號等計算時，將屏幕display數(shù)進行緩存
        if userIsInTheMiddleOfTyping {
            brain.setOperand(displayVaule)
        }
        //標(biāo)識用戶停止鍵入
        userIsInTheMiddleOfTyping = false
        //那么讓model執(zhí)行數(shù)學(xué)運算符判斷，將輸入值sender標(biāo)題→mathmaticalSymbol數(shù)學(xué)符號→brain執(zhí)行運算函數(shù)
        if let mathmaticalSymbol = sender.currentTitle {
            brain.performOperation(mathmaticalSymbol)
        }
        //那么讓我們將model中的結(jié)果從堆中復(fù)制給view中result，在view中將其復(fù)制給屏幕（label）
        if let result = brain.result {
            displayVaule = result
        }
    }
}
//
//  CalculatorBrain.swift
//  calculator
//
//  Created by 郭百度 on 2017/9/23.
//  Copyright ? 2017年 Luke. All rights reserved.
//

import Foundation
//func changeSign(operand: Double) -> Double {
//    return -operand
//}
//func multiply(op1:Double, op2:Double) -> Double{
//    return op1 * op2
//}


struct CalculatorBrain {
    //構(gòu)建私有變量accumulator雙精度蓄存器
    private var accumulator: Double?
    
    private enum Operation {
        case constant(Double)
        case unaryOperation((Double) -> Double)
        case binaryOperation((Double,Double) -> Double)
        case equals
    }
    
    //生命私有變量operations（加了s）為字典，為字典賦值
    private var operations: Dictionary<String,Operation> = [
        "π" : Operation.constant(Double.pi),
        "e" : Operation.constant(M_E),//M_E,
        "√" : Operation.unaryOperation(sqrt),//sqrt,
        "cos" : Operation.unaryOperation(cos), //cos
        "±" : Operation.unaryOperation({-$0}), //±
        "+" : Operation.binaryOperation({ $0 + $1} ), // x *
        "-" : Operation.binaryOperation({ $0 - $1 }), // x *
        "×" : Operation.binaryOperation({ $0 * $1 }), // x *
        "÷" : Operation.binaryOperation({ $0 / $1 }), // x *
        "=" : Operation.equals
    ]

    //構(gòu)建多變函數(shù)執(zhí)行運算，輸入值忽略標(biāo)簽，變量symbol符號，類型為字符串
    mutating func performOperation(_ symbol: String) {
        //如果字典查詢operations[symbol]有值的話，將其賦值給變量operation，沒有則跳過整個枚舉
        if let operation = operations[symbol] {
            //對賦值后的operation進行解析
            switch operation {
                //聲明字典內(nèi)提取為“值”value，將字典內(nèi)常數(shù)值直接給蓄存器
                case .constant(let value):
                    accumulator = value
                //聲明字典內(nèi)提取為“函數(shù)”function，蓄存器中若不為nil，則進行sqrt、cos等枚舉的函數(shù)運算，否則跳過
                case .unaryOperation(let function):
                    if accumulator != nil {
                        accumulator = function(accumulator!)
                    }
                //聲明字典內(nèi)提取為“二元函數(shù)運算”同樣適用function（不同枚舉不沖突），蓄存器中若不為nil，則進行枚舉binaryOperation字典中的運算公式，運算函數(shù)為function，為區(qū)別，此處與官方教程不同使用了function2和functionVaule更易懂
                case .binaryOperation(let functionVaule):
                    if accumulator != nil {
                        pendingBinaryOperation = PendingBinaryOperation(funciton2: functionVaule, firstOperand: accumulator!)
                        accumulator = nil
                    }
                case .equals:
                    performPendingBinaryOperation()
            }
        } else {
            //之前一個用x當(dāng)乘號一個用×當(dāng)乘號……然后乘法一直沒用……坑
            print("沒有找到枚舉值")
        }
    }
    
    private mutating func performPendingBinaryOperation() {
        if pendingBinaryOperation != nil && accumulator != nil {
            accumulator = pendingBinaryOperation!.perform(with: accumulator!)
            pendingBinaryOperation = nil
        }
    }
    
    private var pendingBinaryOperation: PendingBinaryOperation?
    private struct PendingBinaryOperation {
        //此處聲明了二元函數(shù)運算中為兩個雙精度變量輸入及一個雙精度變量輸出
        let funciton2 : (Double,Double) -> Double
        let firstOperand : Double
        
        func perform(with secondOperand:Double) -> Double {
            //此處調(diào)用了function為枚舉計算公式，在swift中使用$0、$1...按順序輸入變量
            return funciton2(firstOperand,secondOperand)
        }
    }
    
    mutating func setOperand(_ operand:Double) {
        accumulator = operand
    }
    //輸出結(jié)果
    var result: Double? {
        get {
            return accumulator
        }
    }
}

引用
Swift 語言 iOS10 開發(fā) 斯坦福(Stanford) CS193p 公開課（1）
Swift 語言 iOS10 開發(fā) 斯坦福(Stanford) CS193p 公開課（2）
Swift 語言 iOS10 開發(fā) 斯坦福(Stanford) CS193p 公開課（3）