斯坦福大学第二课学习笔记-MyFirstIosApp

本次视频主要是完成一个简易计算器的雏形，其中的知识点如下所示

1. 学习storyborad中view层控件拖拽定义变量的用法（.h)，控件拖拽定义方法的用法（.m)
2. 学习了私有变量和方法的定义方式
3. 学习了创建model的方法
4. 学习几种常见的oc类

 https://files.cnblogs.com/NeverLand-Lee/Caculator.zip

CalculatorBrain.h

#import <Foundation/Foundation.h>
简单定义两个共有方法
@interface CalculatorBrain : NSObject
-(void)pushOperand:(double)operand;
-(double)performOperation:(NSString*)operation;

@end

CalculatorBrain.m

#import "CalculatorBrain.h"

@interface CalculatorBrain()
定义私有变量，可变数组
@property(nonatomic,strong) NSMutableArray* operandStack;

@end

@implementation CalculatorBrain
防止bug的写法
@synthesize operandStack = _operandStack;
重写它的get方法，在其中进行延迟初始化
-(NSMutableArray*) operandStack
{
    //alloc the _operandStack
    if(_operandStack == nil){
        _operandStack = [[NSMutableArray alloc]init];
    }
    return _operandStack;
}

-(void)setOperandStack:(NSMutableArray *)operandStack
{
    _operandStack = operandStack;
}

-(void)pushOperand:(double)operand
{
　　将double类型转换为object类型，并放入数组
    NSNumber* operandObject = [NSNumber numberWithDouble:operand];
    
    //change operand to a object
    [self.operandStack addObject:operandObject];
}

-(double)popOperand
{
　　将数组的中的元素取出，并进行判断是否为空
    NSNumber* operandObjct = [self.operandStack lastObject];
    
    //make sure the array is not nil
    if (operandObjct) {
        [self.operandStack removeObject:operandObjct];
    }
    return [operandObjct doubleValue];
}


-(double)performOperation:(NSString*)operation
{
　　进行操作数的判断，判断完成后进行计算，并且将计算结果压回数组，并且返回结果
    double result = 0;
    
    if([@"+" isEqualToString:operation]){
        result = [self popOperand] + [self popOperand];
    }else if([@"*" isEqualToString:operation]){
        result = [self popOperand] * [self popOperand];
    }

    //push it to array for a loop
    [self pushOperand:result];
    
    return result;
    
}

@end

CalculatorViewController.h

//
//  CalculatorViewController.h
//  Caculator
//
//  Created by 建国 李 on 12-5-13.
//  Copyright (c) 2012年 __MyCompanyName__. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface CalculatorViewController : UIViewController
通过拖拽的方式定义的label，因为view上面已经是strong所以这里是weak，并且最好所有界面上的控件都是weak
@property (weak, nonatomic) IBOutlet UILabel *display;

@end

CalculatorViewController.m

//
//  CalculatorViewController.m
//  Caculator
//
//  Created by 建国 李 on 12-5-13.
//  Copyright (c) 2012年 __MyCompanyName__. All rights reserved.
//

#import "CalculatorViewController.h"
//import is in the .m file not .h file
引入model文件，注意并不是在.h文件中引入，而是在哪调用（一般为m文件）在哪引用

#import "CalculatorBrain.h"


@interface CalculatorViewController ()

//private var decide the user is or not input
判断用户是否开始输入了

@property(nonatomic) BOOL userIsInTheMiddleOfEnterANumber;
定义一个私有的model对象
@property(nonatomic,strong) CalculatorBrain* brain;

@end

@implementation CalculatorViewController
@synthesize display = _display;
@synthesize userIsInTheMiddleOfEnterANumber;
@synthesize brain = _brain;


-(CalculatorBrain*)brain{
进行延迟初始化
    if(!_brain){
        _brain = [[CalculatorBrain alloc]init];
    }
    
    return _brain;
}


- (IBAction)digitPressed:(UIButton*)sender {
//    [[self display] setText:[[[self display] text] stringByAppendingString:[sender currentTitle]]];
    当用户开始输入的时候，进行label数字叠加
    NSString* dight = [sender currentTitle];
    if(userIsInTheMiddleOfEnterANumber){
        self.display.text = [self.display.text stringByAppendingString:dight];
    }else {
        self.display.text = dight;
        self.userIsInTheMiddleOfEnterANumber = YES;
    }
    
    
    
 }

- (IBAction)enterPressed {
    
　　用户点击erter按钮，将数字压入数组，并且将用户输入状态改为结束。
    [self.brain pushOperand:[self.display.text doubleValue]];
    self.userIsInTheMiddleOfEnterANumber = NO;
    
    
}

- (IBAction)operationPressed:(UIButton *)sender {
    
    //userIsInTheMiddleOfEnterANumber = yes
　　当用户输入完成数字的时候点击了操作符，帮助用户自动将数字装入数组

    if(self.userIsInTheMiddleOfEnterANumber){
        [self enterPressed];
    }
　　调用model进行计算，并且将结果转换为string显示在label上。
    double result = [self.brain performOperation:sender.currentTitle];
    NSString* resultString = [NSString stringWithFormat:@"%g",result];
    self.display.text = resultString;
    
    
}




@end