[Stanford 2011] Ordinary Calculator（By myself）

说明：

前面的RPN计算器是按照stanford课程做的，是后缀表达式的计算。现在这个计算器是自己做的。这个是一般的计算器，即中缀表达式的计算，而且把计算过程也显示在屏幕上，

设计方法：

在Model里用了两个栈，一个是数字栈，一个是操作符栈。如果压入数字的话，检查操作符栈的最顶端元素是不是乘号和除号，如果是乘号和除号则出栈计算乘除结果；如果操作符栈栈顶是加减号，直接把数字压入数字栈。最终，在按下“等号键”计算结果时，操作符栈中只有加号和减号，此时对数字栈和操作符栈依次出栈计算最终结果。

Final “View” ：

the codes of the “Model”：

//  OrdinaryCalculatorBrain.h
//  OrdinaryCalculator
//
//  Created by Lvxy on 10/4/14.
//  Copyright (c) 2014 Lvxy. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface OrdinaryCalculatorBrain : NSObject
-(void)pushOperation:(NSString *)operation; // + - * /
-(void)pushOperand:(double)operand;
-(double)equal;
-(void)clearAll;
@end

//  OrdinaryCalculatorBrain.m
//  OrdinaryCalculator
//
//  Created by Lvxy on 10/4/14.
//  Copyright (c) 2014 Lvxy. All rights reserved.
//

#import "OrdinaryCalculatorBrain.h"
@interface OrdinaryCalculatorBrain()
@property (nonatomic,strong)NSMutableArray *numberStack;
@property(nonatomic,strong)NSMutableArray *operationStack;
@end

@implementation OrdinaryCalculatorBrain
@synthesize numberStack = _numberStack;
@synthesize operationStack = _operationStack;

-(NSMutableArray*)numberStack{
    if (_numberStack==) {
        _numberStack = [[NSMutableArray alloc]init];
    }
    return _numberStack;
}
-(NSMutableArray*)operationStack{
    if(_operationStack==){
        _operationStack = [[NSMutableArray alloc]init];
    }
    return _operationStack;
}
-(void)pushOperation:(NSString *)operation{ // + - * /
    [self.operationStack addObject:operation];

}
-(void)pushOperand:(double)operand{
    NSString *lastOperation = [self.operationStack lastObject];
    if (lastOperation==nil || [lastOperation isEqualToString:@"+" ]||[lastOperation isEqualToString:@"-"]){
        [self.numberStack addObject:[NSNumber numberWithDouble:operand]];
    }
    else if([lastOperation isEqualToString:@"*" ]||[lastOperation isEqualToString:@"/"]){
        [self.operationStack removeLastObject];
        double num2 = operand;
        NSNumber *lastNumber = [self.numberStack lastObject];
        if(lastNumber)[self.numberStack removeLastObject];
        double num1 = [lastNumber doubleValue];
        if ([lastOperation isEqualToString:@"*" ]) {
            [self.numberStack addObject:[NSNumber numberWithDouble:num1*num2]];
        }else if([lastOperation isEqualToString:@"/" ]){
            [self.numberStack addObject:[NSNumber numberWithDouble:num1/num2]];
        }
    }
}
-(double)equal{
    double result = ;
    while ([self.operationStack lastObject]!=nil) {
        NSString *lastOperation = [self.operationStack lastObject];
        if (lastOperation) [self.operationStack removeLastObject];
        double num1 = result;
        NSNumber *lastNumber = [self.numberStack lastObject];
        if(lastNumber)[self.numberStack removeLastObject];
        double num2 = [lastNumber doubleValue];
        if ([lastOperation isEqualToString:@"+" ]) {
            result = num1+num2;
        }else if([lastOperation isEqualToString:@"-" ]){
            result = num1-num2;
        }
    }
    NSNumber *lastNumber = [self.numberStack lastObject];
    if(lastNumber)[self.numberStack removeLastObject];
    double num2 = [lastNumber doubleValue];
    result += num2;
    return result;

}
-(void)clearAll{
    if (self.numberStack) {
        [self.numberStack removeAllObjects];
    }
    if(self.operationStack){
        [self.operationStack removeAllObjects];
    }
}
@end

the codes of the “controller”：

//  CalculatorViewController.h
//  OrdinaryCalculator
//
//  Created by Lvxy on 10/4/14.
//  Copyright (c) 2014 Lvxy. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface CalculatorViewController : UIViewController
@property (weak, nonatomic) IBOutlet UILabel *display;

@end

//  CalculatorViewController.m
//  OrdinaryCalculator
//
//  Created by Lvxy on 10/4/14.
//  Copyright (c) 2014 Lvxy. All rights reserved.
//

#import "CalculatorViewController.h"
#import "OrdinaryCalculatorBrain.h"
@interface CalculatorViewController ()
@property (nonatomic,strong)OrdinaryCalculatorBrain *brain;
@property(nonatomic)BOOL userIsInTheMiddleOfEnteringANumber;
@property(nonatomic)NSString *currentDigit;
@property(nonatomic)BOOL IsNotFirstPressed;
@end

@implementation CalculatorViewController
@synthesize display = _display;
@synthesize brain = _brain;
@synthesize userIsInTheMiddleOfEnteringANumber=_userIsInTheMiddleOfEnteringANumber;
@synthesize IsNotFirstPressed=_IsNotFirstPressed;
-(OrdinaryCalculatorBrain*)brain{
  if(_brain==nil)
      _brain = [[OrdinaryCalculatorBrain alloc] init];
  return _brain;
}
- (IBAction)digitPressed:(UIButton *)sender {
    if(self.IsNotFirstPressed==){
        self.display.text = @"";
        self.IsNotFirstPressed = ;
    }

    NSString *digit = sender.currentTitle;
    self.display.text = [self.display.text stringByAppendingString:digit];
    if (self.userIsInTheMiddleOfEnteringANumber) {
        self.currentDigit = [self.currentDigit stringByAppendingString:digit];
    }else{
        self.currentDigit = digit;
        self.userIsInTheMiddleOfEnteringANumber = ;
    }

}

- (IBAction)operationPressed:(UIButton *)sender {
    [self.brain pushOperand:[self.currentDigit doubleValue]];
    self.currentDigit = @"";
    self.display.text = [self.display.text stringByAppendingString:sender.currentTitle];
    [self.brain pushOperation:sender.currentTitle];
    self.userIsInTheMiddleOfEnteringANumber = ;

}
- (IBAction)ClearPressed {
    [self.brain clearAll];
    self.userIsInTheMiddleOfEnteringANumber = ;
    self.IsNotFirstPressed = ;
    self.display.text = @"";
}

- (IBAction)equalPressed:(UIButton *)sender {
    [self.brain pushOperand:[self.currentDigit doubleValue]];
    self.currentDigit = @"";
    double result = [self.brain equal];
    self.display.text = [[self.display.text stringByAppendingString:@"="]stringByAppendingString:[NSString stringWithFormat:@"%g",result]];
    self.userIsInTheMiddleOfEnteringANumber = ;
}

@end