思路解构

要学会写计算器，必须要学会用栈来实现四则运算，同时要实现复杂运算的前提，就增加括号、小数点情况的判断来处理。

这里提供两篇博客参考：
四则运算
栈的四则运算（带小数点和括号）

然后根据OC的特性，（Objective-C中没有栈这种数据结构）考虑用可变数组来直接进行对栈的模拟，操作更简洁。

当然，也可以直接用C来进行算法部分，OC的环境下运行C完全没有问题。

MVC

这里使用MVC设计模式来对计算器进行设计。
MVC的具体介绍可在这里了解：MVC模式基础

显然对于算法部分一定是放在Model中进行数据处理，计算器显示屏与计算器按钮的布局写在View中，当需要在viewController布局View时，View内的布局方法被调用。ViewController就负责转发请求，处理请求。

Masonry布局

Masonry安装以及基本使用
这次使用了Masonry框架来对计算器的各个按钮元件设置位置，更方便更快捷而且不会因为机型更迭而失效或出现乱位。

 _roundButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];[_roundButton addTarget:self action:@selector(pressButton:) forControlEvents:UIControlEventTouchUpInside];[self addSubview:_roundButton];//设置按钮圆角_roundButton.layer.cornerRadius = 45;//边框宽度_roundButton.layer.borderWidth = 1;[_roundButton setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];_roundButton.titleLabel.font = [UIFont systemFontOfSize:45];[_roundButton mas_makeConstraints:^(MASConstraintMaker *make) {make.top.equalTo(@(self.frame.size.height/3 + 100 * (i-1) + 80));make.left.equalTo(@(10 + (j-1) * 100));make.height.equalTo(@90);make.width.equalTo(@90);

实际效果：

设计时的问题解决

计算表达式：用UILabel去充当计算器显示屏，每次按下一个按钮就用传值从View传到Controller，处理传来的值并刷新Label，就可以实现向计算器不断输入数据.
刷新时使用下面方法：

- (void)reloadInputViews API_AVAILABLE(ios(3.2));
//具体使用：[_mainView.numLabel reloadInputViews];
//_mianView.numLabel是需要刷新的label

计算结果处理：
计算结果如果是用double类型转换为字符串再放到label上显示，会出现多余0的情况，可以这么处理：

lastString = [NSMutableString stringWithFormat:@"%@", @(testString.floatValue)];

用floatValue属性对testString处理来得到lastString，注意使用这一操作时需要将数据转成字符串testString。

限制输入：对于计算器，人类所能写出来的算法只能计算正确无误的表达式，如果输入字符串的表达式不是符合数学上的规则，就会导致算法无法正常计算，程序崩溃，我们就可以用一些合适的属性作为标志，通过判断来限制输入（也可以通过判断在合适的时机将label.text置为error）。

下面列出了一部分我写计算器时所遵循的限制：

加减乘除：运算符号不能打头不能结尾，不能连续输入运算符，需要输入数字来保证运算符被分隔
小数点：不能打头不能结尾，不能连续输入小数点，不能跟随运算符或者括号出现
括号：不能左右括号数量不匹配，左括号左边不能连运算符号之外的字符，右括号右边不能连运算符号之外的字符。

代码

View

这是布局按钮的完整代码

//布局按钮for (int i = 1; i <= 4; i++) {for (int j = 1; j <=4; j++) {_roundButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];[_roundButton addTarget:self action:@selector(pressButton:) forControlEvents:UIControlEventTouchUpInside];[self addSubview:_roundButton];//设置按钮圆角_roundButton.layer.cornerRadius = 45;//边框宽度_roundButton.layer.borderWidth = 1;[_roundButton setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];_roundButton.titleLabel.font = [UIFont systemFontOfSize:45];[_roundButton mas_makeConstraints:^(MASConstraintMaker *make) {make.top.equalTo(@(self.frame.size.height/3 + 100 * (i-1) + 80));make.left.equalTo(@(10 + (j-1) * 100));make.height.equalTo(@90);make.width.equalTo(@90);}];if (i == 1 && j != 4) {_roundButton.backgroundColor = [UIColor colorWithRed:0.608 green:0.608 blue:0.608 alpha:1];[_roundButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];if (j == 1) {[_roundButton setTitle:@"AC" forState:UIControlStateNormal];_roundButton.titleLabel.textColor = [UIColor blackColor];}if (j == 2) {[_roundButton setTitle:@"(" forState:UIControlStateNormal];_roundButton.titleLabel.textColor = [UIColor blackColor];}if (j == 3) {[_roundButton setTitle:@")" forState:UIControlStateNormal];_roundButton.titleLabel.textColor = [UIColor blackColor];}_roundButton.tag = 110 + j;}if (i == 2 && j != 4) {_roundButton.backgroundColor = [UIColor darkGrayColor];if (j == 1) {[_roundButton setTitle:@"7" forState:UIControlStateNormal];}if (j == 2) {[_roundButton setTitle:@"8" forState:UIControlStateNormal];}if (j == 3) {[_roundButton setTitle:@"9" forState:UIControlStateNormal];}_roundButton.tag = 106 + j;}if (i == 3 && j != 4) {_roundButton.backgroundColor = [UIColor darkGrayColor];if (j == 1) {[_roundButton setTitle:@"4" forState:UIControlStateNormal];}if (j == 2) {[_roundButton setTitle:@"5" forState:UIControlStateNormal];}if (j == 3) {[_roundButton setTitle:@"6" forState:UIControlStateNormal];}_roundButton.tag = 103 + j;}if (i == 4 && j != 4) {_roundButton.backgroundColor = [UIColor darkGrayColor];if (j == 1) {[_roundButton setTitle:@"1" forState:UIControlStateNormal];}if (j == 2) {[_roundButton setTitle:@"2" forState:UIControlStateNormal];}if (j == 3) {[_roundButton setTitle:@"3" forState:UIControlStateNormal];}_roundButton.tag = 100 + j;}if (j == 4) {_roundButton.backgroundColor = [UIColor orangeColor];if (i == 1) {[_roundButton setTitle:@"÷" forState:UIControlStateNormal];_roundButton.tag = 114;} else if (i == 2) {[_roundButton setTitle:@"×" forState:UIControlStateNormal];_roundButton.tag = 115;} else if (i == 3) {[_roundButton setTitle:@"－" forState:UIControlStateNormal];_roundButton.tag = 116;} else {[_roundButton setTitle:@"+" forState:UIControlStateNormal];_roundButton.tag = 117;}}}}//最后一行   一个零 一个点 一个等号for (int k = 0; k < 3; k++) {if (k == 0) {_roundButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];[_roundButton addTarget:self action:@selector(pressButton:) forControlEvents:UIControlEventTouchUpInside];[self addSubview:_roundButton];//设置按钮圆角_roundButton.layer.cornerRadius = 45;//边框宽度_roundButton.layer.borderWidth = 1;[_roundButton setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];_roundButton.titleLabel.font = [UIFont systemFontOfSize:45];[_roundButton mas_makeConstraints:^(MASConstraintMaker *make) {make.top.equalTo(@(self.frame.size.height/3 + 100 * 4 + 80));make.left.equalTo(@(10 + 0 * 100));make.height.equalTo(@90);make.width.equalTo(@190);}];[_roundButton setTitle:@"0" forState:UIControlStateNormal];_roundButton.backgroundColor = [UIColor darkGrayColor];_roundButton.tag = 100;} else {_roundButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];[_roundButton addTarget:self action:@selector(pressButton:) forControlEvents:UIControlEventTouchUpInside];[self addSubview:_roundButton];//设置按钮圆角_roundButton.layer.cornerRadius = 45;//边框宽度_roundButton.layer.borderWidth = 1;[_roundButton setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];_roundButton.titleLabel.font = [UIFont systemFontOfSize:45];[_roundButton mas_makeConstraints:^(MASConstraintMaker *make) {make.top.equalTo(@(self.frame.size.height/3 + 100 * 4 + 80));make.left.equalTo(@(10 + (k+1) * 100));make.height.equalTo(@90);make.width.equalTo(@90);}];if (k == 1) {[_roundButton setTitle:@"." forState:UIControlStateNormal];_roundButton.backgroundColor = [UIColor darkGrayColor];_roundButton.tag = 110;}if (k == 2) {[_roundButton setTitle:@"=" forState:UIControlStateNormal];_roundButton.backgroundColor = [UIColor orangeColor];_roundButton.tag = 118;}}}

Model

#import "CalculatorModel.h"@implementation CalculatorModel- (void) pushNum:(double)num {if (_numArray.count == 50) {NSLog(@"进栈失败");return;}//NSLog(@"%f", num);[_numArray addObject:[NSString stringWithFormat:@"%f", num]];return;
}- (void) pushChar: (char) c {if (_strArray.count == 50) {NSLog(@"进栈失败");return;}//NSLog(@"%c", c);[_strArray addObject:[NSString stringWithFormat:@"%c", c]];return;
}//字符串转数字
- (double) transNum: (NSString*) string {//NSLog(@"%c", [string characterAtIndex:0]);int minus = 0;double result;if ([string characterAtIndex:0] == '-') {minus = 1;}if (minus == 0) {int i = 0;double x = 0;while ([string characterAtIndex:i] >= '0' &&[string characterAtIndex:i] <= '9' &&i < string.length) {x *= 10 ;x += (double) [string characterAtIndex:i] - '0';//NSLog(@"%f", x);++i;}//存在小数点if (i < string.length && [string characterAtIndex:i] == '.') {double m = 0.1;i++;while (i < string.length) {x += ((double) [string characterAtIndex:i] - '0') * m;m *= 0.1;++i;}}result = x;} else {                //int i = 1;double x = 0;while ([string characterAtIndex:i] >= '0' &&[string characterAtIndex:i] <= '9' &&i < string.length) {x *= 10;x += (double)[string characterAtIndex:i] - '0';++i;}//存在小数点if (i < string.length && [string characterAtIndex:i] == '.') {double m = 0.1;++i;while (i < string.length) {x += ((double)[string characterAtIndex:i] - '0') * m;m *= 0.1;++i;}}result = x;}if (minus == 0) {return  result;} else {return  -result;}}- (double) popNum {double temp = [self transNum:_numArray[_numArray.count - 1]];[_numArray removeLastObject];return temp;
}- (char) popChar {char temp = [_strArray[_strArray.count - 1] characterAtIndex:0];[_strArray removeLastObject];return temp;
}//返回数字栈栈顶
- (double) topNum {return [self transNum:_numArray[_numArray.count - 1]];
}//返回符号栈栈顶
- (char) topChar {return [_strArray[_strArray.count - 1] characterAtIndex:0];
}//比较符号优先级
- (NSInteger) compare:(char) str {if (str == '+' || str == '-') {return 1;} else if (str == '*' || str == '/') {return 2;} else {return 0;}
}//计算函数
- (double) counter:(double) first :(double) second :(char) counterStr {double ans = 0.0;if (counterStr == '+') {ans = first + second;} else if (counterStr == '-') {ans = second - first;} else if (counterStr == '*') {ans = first * second;} else {ans = second / first;}return ans;
}- (NSInteger) emptyNum{NSInteger cnt = _numArray.count;[_numArray removeAllObjects];return cnt;
}- (NSInteger) emptyChar {NSInteger cnt = _strArray.count;[_strArray removeAllObjects];return cnt;
}@end

计算表达式：

- (void) calculation {CalculatorModel* Model = [[CalculatorModel alloc]init];Model.numArray = [[NSMutableArray alloc]init];Model.strArray = [[NSMutableArray alloc]init];Model.expression = [NSMutableString stringWithString:_mainView.numLabel.text];NSMutableString* newString = [NSMutableString stringWithString:Model.expression];[newString appendString:@"#"];char* cStr = (char*)[newString UTF8String];/*          NSMutableArray* arrayStack = [[NSMutableArray alloc]init];for (int i = 0; i < Model.expression.length; i++) {if (cStr[i] == '+' || cStr[i] == '-') {if ([arrayStack.lastObject isEqualToString:@"*"] ||[arrayStack.lastObject isEqualToString:@"/"]) {}} else if (cStr[i] == '*' || cStr[i] == '/') {} else if (cStr[i] == ')') {} else {}}*/int index = 0;double x = 0;double numberFirst, numberSecond;char testChar;double lastResult = 0.0;while (cStr[index] != '#') {x = 0;//判断是数字入数字栈if (cStr[index] >= '0' && cStr[index] <= '9') {while (cStr[index] >= '0' && cStr[index] <= '9') {x = x * 10;x = x + cStr[index] - '0';index++;}//判断小数点if (cStr[index] == '.') {double t = 0.1;index++;while (cStr[index] >= '0' && cStr[index] <= '9') {x += (t * (cStr[index] - '0'));t *= 0.1;index++;}}//将得到的数字送进数字栈[Model pushNum:x];continue;}//判断是符号送进符号栈,送符号进栈时确保符号栈空if (Model.strArray.count == 0 && (cStr[index] == '+' || cStr[index] == '-' || cStr[index] == '*' || cStr[index] == '/' || cStr[index] == '(' || cStr[index] == ')')) {[Model pushChar:cStr[index]];index++;continue;}//左括号直接入栈if (cStr[index] == '(') {[Model pushChar:cStr[index]];index++;continue;}//右括号需要循环取出符号栈的符号，同时循环每次取两个数字栈的数字运算后，放回数字栈，直到从符号栈取出左括号if (cStr[index] == ')') {while ( [Model topChar] != '(') {testChar = [Model popChar];numberFirst = [Model popNum];numberSecond = [Model popNum];lastResult = [Model counter:numberFirst :numberSecond :testChar];//计算结果入数字栈[Model pushNum:lastResult];}//左括号出栈[Model popChar];index++;continue;}//入符号栈if ([Model compare:cStr[index]] <= [Model compare:[Model topChar]]) {testChar = [Model popChar];numberFirst = [Model popNum];numberSecond = [Model popNum];lastResult = [Model counter:numberFirst :numberSecond :testChar];[Model pushNum:lastResult];}[Model pushChar:cStr[index]];index++;}//若是符号栈还不为空while (Model.strArray.count > 0) {testChar = [Model popChar];numberFirst = [Model popNum];numberSecond = [Model popNum];lastResult = [Model counter:numberFirst :numberSecond :testChar];[Model pushNum:lastResult];}NSString* testString = [NSString stringWithFormat:@"%f", lastResult];float k = (float) lastResult;int n = (int) k;NSMutableString* lastString;if ((k - n) <= 0.001 && k >= n) {lastString = [NSMutableString stringWithFormat:@"%d", n];} else if((n-k) <= 0.001 && k < n) {lastString = [NSMutableString stringWithFormat:@"%d", n];} else {if (k>=n) {lastString = [NSMutableString stringWithFormat:@"%@", @(testString.floatValue)];} else {lastString = [NSMutableString stringWithFormat:@"%@", @(testString.floatValue)];}}_mainView.numLabel.text = lastString;[_mainView.numLabel reloadInputViews];_ACSign = 0;
}

这次的计算器bug频出，究其原因是在写限制输入的时候没有构思好就写，导致后面bug改完一个，新的就又漏出来，必要处注释缺少。以后的项目会越来越难，必须认真对待，少写bug，改正坏习惯。

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