• iOS——仿写计算器

    四则运算：中缀表达式转后缀表达式+后缀表达式求值

    实现四则运算的算法思路是：首先输入的是中缀表达式的字符串，然后将其转为计算机可以理解的后缀表达式，然后将后缀表达式求值：
    中缀转后缀表达式思路参考：《数据结构》：中缀表达式转后缀表达式 + 后缀表达式的计算
    在该思路的基础上，会遇见以下几个问题：

    1. 输入多位数时无法识别出该多位数，可能求值时计算成好几位一位数。我的解决方法是将输入的数字使用",“分隔开，因为每两个相邻的运算符之间只会有一个数，所以在转为后缀表达式时，每当遍历到的字符是一个运算符，就再为存储我们得到的后缀表达式的那个数组中添加一个”,“将数字分隔开，然后在后缀求值的部分，每当读取到一个”,“，就continue掉，然后在读到数字的时候，就先定义一个动态数组，然后使用一个while循环一直循环将当前数字存入数组中，直到遍历到的元素是下一个”,"，此时就跳出循环，然后将该动态数组存入栈中，实现多位数的计算。
    2. 小数点的判断：小数点的判断和多位数一样，将小数点的判定条件和数字一样，存入动态数组时也是一样。存入数组后，我们使用c语言中的strtod函数可以将一个字符串识别为浮点数，便可以很简单的完成小数点的读取。
    3. 括号的判断：括号的判断在这里是一个非常复杂的点：首先在转化为后缀表达式的部分，如果遇到的是左括号，就直接入栈（注：左括号入栈后优先级降至最低）。如果遇到的字符为右括号，就直接出栈，并将出栈字符依次送入后缀表达式，直到栈顶字符为左括号（左括号也要出栈，但不送入后缀表达式）。总结就是：只要满足栈顶为左括号即可进行最后一次出栈。
    4. 负数的判断：对于负数的判断，我的思路是将原本的中缀表达式理解为：-x = (0-x)来进行转化后缀表达式的操作。即在将当前字符串元素传入中缀转后缀表达式的函数中时，判断当前元素是否是"-“，然后判断该元素的上一个元素是否为运算符/括号或者该元素是否是字符串的第一个元素，如果是，就可以将该字符串的这一部分理解为负数。找到为负数的”-“后，首先不将该”-“传入转后缀的函数，而是先依次将”(“,“0"传入，然后再传入当前的”-”，然后再使用一个while循环依次将负数的数字部分的元素传入（记得此时也要一直更改着遍历字符串的下标位置），直到读到的元素为运算符/括号时跳出循环，然后再传入一个")"到转后缀的函数中，至此，我们得到的后缀表达式就是可以正确计算负数的后缀表达式了。然后再计算后缀表达式的部分不用修改，因为负数部分会计算为（0-x）的。
      以下是我四则运算部分的代码实现：
    //定义一个全局变量n，用于记录后缀表达式数组的下标
static int n = 0;

//栈的定义和初始化以及入栈出栈等操作
typedef struct result {
    char stack[10000];
    int top;
    char nBoLan[10000];
}Result;

Result* CreatStack(void) {
    Result *stack = (Result*)malloc(sizeof(Result));
    stack->top = -1;
    return stack;
}

void PushStack(Result *obj, char val) {
    obj->stack[++obj->top] = val;
}

void PopStack(Result *obj) {
    if (obj->top >= 0) {
        obj->top--;
    }
}

char GetTopStack(Result *obj) {
    if (obj->top >= 0) {
        return obj->stack[obj->top];
    }
    return 0;
}

//将中缀表达式转为后缀表达式
void caoZuoStack(char a, Result *obj) {
    if (a == '+' || a == '-') {
        if (obj->stack[obj->top] == '-') {
            while(obj->stack[obj->top] != '(' && obj->top >= 0) {
                obj->nBoLan[n++] = GetTopStack(obj);
                PopStack(obj);
            }
            PushStack(obj, a);
            obj->nBoLan[n++] = ',';
        } else if (obj->stack[obj->top] == '(') {
            PushStack(obj, a);
            obj->nBoLan[n++] = ',';
        } else if (obj->stack[obj->top] == '*' || obj->stack[obj->top] == '/') {
            while (obj->stack[obj->top] != '(' && obj->top >= 0) {
                obj->nBoLan[n++] = GetTopStack(obj);
                PopStack(obj);
            }
            PushStack(obj, a);
            obj->nBoLan[n++] = ',';
        } else {
            PushStack(obj, a);
            obj->nBoLan[n++] = ',';
        }
    } else if (a == '*' || a == '/'){
        if (obj->stack[obj->top] == '/') {
            obj->nBoLan[n++] = GetTopStack(obj);
            PopStack(obj);
            PushStack(obj, a);
            obj->nBoLan[n++] = ',';
        } else if (obj->stack[obj->top] == '(') {
            PushStack(obj, a);
            obj->nBoLan[n++] = ',';
        } else {
            PushStack(obj, a);
            obj->nBoLan[n++] = ',';
        }
    } else if (a == ')') {
        while(obj->stack[obj->top] != '(') {
            obj->nBoLan[n++] = GetTopStack(obj);
            PopStack(obj);
        }
        PopStack(obj);
    } else if (a == '(') {
        PushStack(obj, a);
    } else if (a != '=' && a != ')' && a != '(') {
        obj->nBoLan[n++] = a;
    }
    if (a == '=') {
        while(obj->top >= 0) {
            obj->nBoLan[n++] = GetTopStack(obj);
            PopStack(obj);
        }
    }
    printf("%s\n", obj->nBoLan);
}

//后缀表达式求值
double evalRPN(char *tokens, int tokensSize){
    int top = -1;
    double stack[100];
    for (int i = 0; i < tokensSize; i++) {
        if (tokens[i] == ',' || tokens[i] == '(' || tokens[i] == ')') {
            continue;
        }
        if (tokens[i] == '+') {
            stack[top - 1] = stack[top] + stack[top - 1];
            top--;
            continue;
        }
        if (tokens[i] == '-') {
            stack[top - 1] = stack[top - 1] - stack[top];
            top--;
            continue;
        }
        if (tokens[i] == '*') {
            stack[top - 1] = stack[top] * stack[top - 1];
            top--;
            continue;
        }
        if (tokens[i] == '/') {
            stack[top - 1] = stack[top - 1] / stack[top];
            top--;
            continue;
        } else {
            int sum = 0;
            char *s = (char*)malloc(sizeof(char) * 2 * (sum+1));
            while (tokens[i] != ',' && tokens[i] != '+' && tokens[i] != '-' && tokens[i] != '*' && tokens[i] != '/' && tokens[i] != '(' && tokens[i] != ')') {
                s[sum++] = tokens[i];
                i++;
            }
            if (tokens[i] == '+' || tokens[i] == '-' || tokens[i] == '*' || tokens[i] == '/' || tokens[i] == '(' || tokens[i] == ')') {
                i--;
            }
            char *t;
            double theNum = strtod(s, &t);
            stack[++top] = theNum;
        }
        continue;
    }
    return stack[top];
}

//将计算器输入的字符串传给上面两个函数
- (double)jiSuan: (NSString*)putInStr {
    NSLog(@"%@", putInStr);
    n = 0;
    Result *obj = CreatStack();
    //对负数进行判断
    for (int i = 0; i < [putInStr length]; i++) {
        if ((i == 0 && [putInStr characterAtIndex:0] == '-') || ([putInStr characterAtIndex:i] == '-' && ([putInStr characterAtIndex:i-1] == '+' || [putInStr characterAtIndex:i-1] == '-' || [putInStr characterAtIndex:i-1] == '*' || [putInStr characterAtIndex:i-1] == '/' || [putInStr characterAtIndex:i-1] == '('))) {
            caoZuoStack('(', obj);
            caoZuoStack('0', obj);
            caoZuoStack('-', obj);
            i++;
            while (([putInStr characterAtIndex:i] >= 48 && [putInStr characterAtIndex:i] <= 57) || [putInStr characterAtIndex:i] == '.') {
                caoZuoStack([putInStr characterAtIndex:i], obj);
                i++;
            }
            caoZuoStack(')', obj);
            i--;
            continue;
        }
        caoZuoStack([putInStr characterAtIndex:i], obj);
    }
    int tokensSize = (int)strlen(obj->nBoLan);
    printf("%lf", evalRPN(obj->nBoLan, tokensSize));
    //返回结果
    return evalRPN(obj->nBoLan, tokensSize);
}

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    计算器的布局及限制

    本次计算机的仿写我使用的是mvc模式，并且布局使用了Masonry框架。

    • 在model层：我使用了一个可变数组来存储表达式以及结果，当在计算器上点击输入表达式时，点击的合法的按钮的会传相应的值到该字符串中，点击AC按钮时将会清空该字符串，点击“=”按钮后将会先计算表达式的结果，然后清空该字符串，然后再将得到的结果传入该字符串。model层和controller层使用KVO传值，但是该KVO传值的监听对象并不是该可变数组对象，因为前面学过KVO只是监听setter方法，但是向可变数组添加元素的方法它不属于setter方法，所以即使你向数组中add多少个元素也不会有监听反应。所以这里我的操作是再model层再声明一个int类型的a属性，并在初始化的时候给其赋值为0，然后使用KVO监听该a属性，在controller层中，每当点击了按钮，就将该a属性自增使得其值改变，由此就可以触发监听事件。在监听事件中，将view层声明的label属性的text属性赋值为该可变字符串，这样就可以实现每当点击按钮，上面的表达式可以随时改变。
      代码实现：
    #import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface Model : NSObject

@property (nonatomic, strong) NSMutableString *StrNum;
@property (nonatomic, assign) int a;

@end

NS_ASSUME_NONNULL_END

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    #import "Model.h"

@implementation Model

- (Model*)init {
    self.a = 0;
    if (self = [super init]) {
        self.StrNum = [[NSMutableString alloc] init];
    }
    return self;
}

@end

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    • 在view层：我使用了一个for循环循环创建button，并为每个button的tag赋值，并使用Masonry框架等对其布局。布局这块直接看代码就行了不多赘述。在view层和controller层之间的交互我是使用了通知传值，在view层将button存入一个字典然后用通知传值传给controller层，在controller中对传来的button的tag值进行判断。
      代码实现：
    #import <UIKit/UIKit.h>
#import "Masonry.h"

NS_ASSUME_NONNULL_BEGIN

@interface View : UIView

@property (nonatomic, strong) UILabel *label;
@property (nonatomic, strong) UIButton *Button;


@end

NS_ASSUME_NONNULL_END

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    #import "View.h"

#import "Masonry.h"

#define MAS_SHORTHAND
#define MAS_SHORTHAND_GLOBALS

@implementation View

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    self.backgroundColor = [UIColor blackColor];
    
    //显示在计算器上方的label，用于显示表达式及结果
    self.label = [[UILabel alloc] init];
    [self addSubview:self.label];
    self.label.textColor = [UIColor whiteColor];
    self.label.textAlignment = NSTextAlignmentRight;
    [self.label mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.mas_equalTo(25);
        make.top.mas_equalTo(270);
        make.height.mas_equalTo(@100);
        make.width.mas_equalTo(360);
    }];
    self.label.font = [UIFont systemFontOfSize:50];
    
    //for循环创建button，button的点击事件用来触发通知传值
    for (int i = 0; i < 5; i++) {
        for (int j = 0; j < 4; j++) {
            self.Button = [UIButton buttonWithType:UIButtonTypeCustom];
            [self addSubview:self.Button];
            [self.Button mas_makeConstraints:^(MASConstraintMaker *make) {
                make.left.mas_equalTo(102 * j + 15);
                make.top.mas_equalTo(102 * i + 375);
                make.width.and.height.mas_equalTo(@90);
            }];
            [self.Button addTarget:self action:@selector(pressPutin:) forControlEvents:UIControlEventTouchUpInside];
            self.Button.layer.cornerRadius = 45;
            self.Button.layer.masksToBounds = YES;
            self.Button.titleLabel.font = [UIFont systemFontOfSize:40];

            self.Button.tag = i * 4 + j;
            if (self.Button.tag == 0) {
                [self.Button setTitle:@"AC" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor grayColor]];
            }
            if (self.Button.tag == 1) {
                [self.Button setTitle:@"(" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor grayColor]];
            }
            if (self.Button.tag == 2) {
                [self.Button setTitle:@")" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor grayColor]];
            }
            if (self.Button.tag == 3) {
                [self.Button setTitle:@"/" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor orangeColor]];
            }
            if (self.Button.tag == 4) {
                [self.Button setTitle:@"7" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor darkGrayColor]];
            }
            if (self.Button.tag == 5) {
                [self.Button setTitle:@"8" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor darkGrayColor]];
            }
            if (self.Button.tag == 6) {
                [self.Button setTitle:@"9" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor darkGrayColor]];
            }
            if (self.Button.tag == 7) {
                [self.Button setTitle:@"*" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor orangeColor]];
            }
            if (self.Button.tag == 8) {
                [self.Button setTitle:@"4" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor darkGrayColor]];
            }
            if (self.Button.tag == 9) {
                [self.Button setTitle:@"5" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor darkGrayColor]];
            }
            if (self.Button.tag == 10) {
                [self.Button setTitle:@"6" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor darkGrayColor]];
            }
            if (self.Button.tag == 11) {
                [self.Button setTitle:@"-" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor orangeColor]];
            }
            if (self.Button.tag == 12) {
                [self.Button setTitle:@"1" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor darkGrayColor]];
            }
            if (self.Button.tag == 13) {
                [self.Button setTitle:@"2" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor darkGrayColor]];
            }
            if (self.Button.tag == 14) {
                [self.Button setTitle:@"3" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor darkGrayColor]];
            }
            if (self.Button.tag == 15) {
                [self.Button setTitle:@"+" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor orangeColor]];
            }
            if (self.Button.tag == 16) {
                [self.Button setTitle:@"0" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor darkGrayColor]];
                [self.Button mas_updateConstraints: ^(MASConstraintMaker *make) {
                    make.left.mas_equalTo(102 * j + 15);
                    make.top.mas_equalTo(102 * i + 375);
                    make.width.mas_equalTo(@192);
                    make.height.mas_equalTo(@90);
                }];
            }
            if (self.Button.tag == 17) {
                [self.Button setTitle:@"." forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor darkGrayColor]];
                [self.Button mas_updateConstraints: ^(MASConstraintMaker *make) {
                    make.left.mas_equalTo(102 * (j+1) + 15);
                    make.top.mas_equalTo(102 * i + 375);
                    make.width.and.height.mas_equalTo(@90);
                }];
            }
            if (self.Button.tag == 18) {
                [self.Button setTitle:@"=" forState:UIControlStateNormal];
                [self.Button setBackgroundColor:[UIColor orangeColor]];
                [self.Button mas_updateConstraints: ^(MASConstraintMaker *make) {
                    make.left.mas_equalTo(102 * (j+1) + 15);
                    make.top.mas_equalTo(102 * i + 375);
                    make.width.and.height.mas_equalTo(@90);
                }];
            }
        }
        
    }
    return self;
}

//通知传值
- (void)pressPutin: (UIButton*)Button {
    //NSLog(@"OK");
    NSDictionary *dict =[NSDictionary dictionaryWithObject:Button forKey:@"btn"];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"NumGo" object:nil userInfo:dict];
}
@end


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    • controller层：在controller层中我要对传来的button的tag进行判断并改变可变数组，并且要对按钮的点击进行限制，而且要将前面我们写过的四则运算式子写在这里。对按钮输入限制的判断：我定义了很多个全局变量，例如fuHaoNum，如果点击了ac按钮，就将其赋为初值0，因为字符串中没有元素时不能输入运算符（负号除外）。如果点击了运算符和括号，就将该值赋为0，因为除了负号外，其他运算符和括号不能连续两个相邻。如果点击了数字，就将该值赋为1，因为数字后面可以跟运算符，如果点击了小数点，就将该值赋为0…由此实现限制。
      代码实现：
    #import "ViewController.h"

#include
#include
#include
#include
#include

@interface ViewController ()

@property (nonatomic, strong) View *aView;
@property (nonatomic, strong) Model *model;

@end

static int pointNum = 0;
static int kuoHaoNum = 0;
static int fuHaoNum = 0;
static int jianHao = 0;
static int numAKuoHao = 1;
static int inKuoHao = 0;
static int dengYu = 0;
static int point = 1;
static int dengYuNum = 0;

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.aView = [[View alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:self.aView];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(pressNum:) name:@"NumGo" object:nil];

    self.model = [[Model alloc] init];
    [self.model addObserver:self forKeyPath:@"a" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:nil];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
    self.aView.label.text = [NSString stringWithFormat:@"%@",self.model.StrNum];
    self.aView.label.adjustsFontSizeToFitWidth = YES;
}

- (void)pressWanCheng {
    [self dismissViewControllerAnimated:YES completion:nil];
}

- (void)pressNum: (NSNotification*)sender{
    UIButton *Button = sender.userInfo[@"btn"];
    if(Button.tag == 0) {
        pointNum = 0;
        kuoHaoNum = 0;
        fuHaoNum = 0;
        jianHao = 0;
        numAKuoHao = 1;
        inKuoHao = 0;
        dengYu = 0;
        point = 1;
        dengYuNum = 0;
        
        NSUInteger a = [self.model.StrNum length];
        [self.model.StrNum deleteCharactersInRange:NSMakeRange(0, a)];
    }
    if (Button.tag == 1) {
        if(numAKuoHao) {
            [self.model.StrNum appendFormat:@"("];
            pointNum = 0;
            kuoHaoNum++;
            fuHaoNum = 0;
            jianHao = 1;
            numAKuoHao = 1;
            inKuoHao = 0;
            dengYu = 0;
            point = 1;
            dengYuNum++;
        } else {
            UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil message:@"输入格式错误" preferredStyle:UIAlertControllerStyleAlert];
            [self presentViewController:alert animated:YES completion:nil];
            [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(pressWanCheng) userInfo:nil repeats:NO];
        }
    }
    if (Button.tag == 2) {
        if(fuHaoNum && inKuoHao && kuoHaoNum != 0) {
            [self.model.StrNum appendFormat:@")"];
            pointNum = 0;
            kuoHaoNum--;
            fuHaoNum = 1;
            jianHao = 1;
            numAKuoHao = 0;
            dengYu = 1;
            point = 1;
            dengYuNum++;
        } else {
            UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil message:@"输入格式错误" preferredStyle:UIAlertControllerStyleAlert];
            [self presentViewController:alert animated:YES completion:nil];
            [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(pressWanCheng) userInfo:nil repeats:NO];
        }
    }
    if (Button.tag == 3) {
        if(fuHaoNum) {
            [self.model.StrNum appendFormat:@"/"];
            pointNum = 0;
            fuHaoNum = 0;
            jianHao = 1;
            numAKuoHao = 1;
            inKuoHao = 1;
            dengYu = 0;
            point = 1;
            dengYuNum++;
        } else {
            UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil message:@"输入格式错误" preferredStyle:UIAlertControllerStyleAlert];
            [self presentViewController:alert animated:YES completion:nil];
            [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(pressWanCheng) userInfo:nil repeats:NO];
        }
    }
    if(Button.tag == 4) {
        [self.model.StrNum appendFormat:@"7"];
        pointNum = 1;
        fuHaoNum = 1;
        jianHao = 2;
        numAKuoHao = 0;
        dengYu = 1;
    }
    if(Button.tag == 5) {
        [self.model.StrNum appendFormat:@"8"];
        pointNum = 1;
        fuHaoNum = 1;
        jianHao = 2;
        numAKuoHao = 0;
        dengYu = 1;
    }
    if(Button.tag == 6) {
        [self.model.StrNum appendFormat:@"9"];
        pointNum = 1;
        fuHaoNum = 1;
        jianHao = 2;
        numAKuoHao = 0;
        dengYu = 1;
    }
    if (Button.tag ==7) {
        if(fuHaoNum) {
            [self.model.StrNum appendFormat:@"*"];
            pointNum = 0;
            fuHaoNum = 0;
            jianHao = 1;
            numAKuoHao = 1;
            inKuoHao = 1;
            dengYu = 0;
            point = 1;
            dengYuNum++;
        } else {
            UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil message:@"输入格式错误" preferredStyle:UIAlertControllerStyleAlert];
            [self presentViewController:alert animated:YES completion:nil];
            [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(pressWanCheng) userInfo:nil repeats:NO];
        }
    }
    if(Button.tag == 8) {
        [self.model.StrNum appendFormat:@"4"];
        pointNum = 1;
        fuHaoNum = 1;
        jianHao = 2;
        numAKuoHao = 0;
        dengYu = 1;
    }
    if(Button.tag == 9) {
        [self.model.StrNum appendFormat:@"5"];
        pointNum = 1;
        fuHaoNum = 1;
        jianHao = 2;
        numAKuoHao = 0;
        dengYu = 1;
    }
    if(Button.tag == 10) {
        [self.model.StrNum appendFormat:@"6"];
        pointNum = 1;
        fuHaoNum = 1;
        jianHao = 2;
        numAKuoHao = 0;
        dengYu = 1;
    }
    if (Button.tag == 11) {
        if ([self.model.StrNum length] == 0) {
            [self.model.StrNum appendFormat:@"-"];
            pointNum = 0;
            fuHaoNum = 0;
            jianHao = 0;
            numAKuoHao = 1;
            dengYu = 0;
            point = 1;
        } else if(jianHao) {
            [self.model.StrNum appendFormat:@"-"];
            pointNum = 0;
            fuHaoNum = 0;
            jianHao--;
            numAKuoHao = 1;
            inKuoHao = 1;
            dengYu = 0;
            point = 1;
            dengYuNum++;
        } else {
            UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil message:@"输入格式错误" preferredStyle:UIAlertControllerStyleAlert];
            [self presentViewController:alert animated:YES completion:nil];
            [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(pressWanCheng) userInfo:nil repeats:NO];
        }
    }
    if(Button.tag == 12) {
        [self.model.StrNum appendFormat:@"1"];
        pointNum = 1;
        fuHaoNum = 1;
        jianHao = 2;
        numAKuoHao = 0;
        dengYu = 1;
    }
    if(Button.tag == 13) {
        [self.model.StrNum appendFormat:@"2"];
        pointNum = 1;
        fuHaoNum = 1;
        jianHao = 2;
        numAKuoHao = 0;
        dengYu = 1;
    }
    if(Button.tag == 14) {
        [self.model.StrNum appendFormat:@"3"];
        pointNum = 1;
        fuHaoNum = 1;
        jianHao = 2;
        numAKuoHao = 0;
        dengYu = 1;
    }
    if (Button.tag == 15) {
        if(fuHaoNum) {
            [self.model.StrNum appendFormat:@"+"];
            pointNum = 0;
            fuHaoNum = 0;
            jianHao = 1;
            numAKuoHao = 1;
            inKuoHao = 1;
            dengYu = 0;
            point = 1;
            dengYuNum++;
        } else {
            UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil message:@"输入格式错误" preferredStyle:UIAlertControllerStyleAlert];
            [self presentViewController:alert animated:YES completion:nil];
            [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(pressWanCheng) userInfo:nil repeats:NO];
        }
    }
    if(Button.tag == 16) {
        [self.model.StrNum appendFormat:@"0"];
        pointNum = 1;
        fuHaoNum = 1;
        jianHao = 2;
        numAKuoHao = 0;
        dengYu = 1;
    }
    if (Button.tag == 17) {
        if(point && fuHaoNum && pointNum) {
            [self.model.StrNum appendFormat:@"."];
            pointNum = 0;
            fuHaoNum = 0;
            jianHao = 0;
            numAKuoHao = 0;
            dengYu = 0;
            point = 0;
        } else {
            UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil message:@"输入格式错误" preferredStyle:UIAlertControllerStyleAlert];
            [self presentViewController:alert animated:YES completion:nil];
            [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(pressWanCheng) userInfo:nil repeats:NO];
        }
    }
    if (Button.tag == 19) {
        if(dengYuNum && kuoHaoNum == 0 && dengYu) {
            [self.model.StrNum appendFormat:@"="];
            NSLog(@"%@", self.model.StrNum);
            double b = [self jiSuan:self.model.StrNum];
            NSUInteger a = [self.model.StrNum length];
            [self.model.StrNum deleteCharactersInRange:NSMakeRange(0, a)];
            [self.model.StrNum appendFormat:@"%.9g", b];
            if ([self.model.StrNum isEqual: @"inf"]) {
                NSUInteger a = [self.model.StrNum length];
                [self.model.StrNum deleteCharactersInRange:NSMakeRange(0, a)];
                [self.model.StrNum appendFormat:@"不能除以0"];
            }
        } else {
            UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil message:@"输入格式错误" preferredStyle:UIAlertControllerStyleAlert];
            [self presentViewController:alert animated:YES completion:nil];
            [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(pressWanCheng) userInfo:nil repeats:NO];
        }
    }
    self.model.a++;
}

/*此处插入上面四则运算的代码*/
    
@end


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    结果：
    在这里插入图片描述
    在这里插入图片描述

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  • 原文地址：https://blog.csdn.net/m0_73348697/article/details/133637486