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-(void)viewDidLoad
{
    //初始化字符串
    self.num1 = [[NSMutableString alloc]init];
    self.num2 = [[NSMutableString alloc]init];
    self.tempStr = [[NSMutableString alloc]init];
 
    
}
//监听数字按钮0-9和点,点的tag为10
//判断输入数字前有几个0,只取一个零,小数点只取一个
-(IBAction)numbers:(id)sender
{
    //处理0的问题
    //以零开头,下次输入的非0,则清空0
     //如果以0.开头,则不清空
    if ([self.tempStr hasPrefix:@"0"] && [sender tag] > 0 && [sender tag] <10 && ![self.tempStr hasPrefix:@"0."])
    {
        self.tempStr = [NSMutableString stringWithString:@""];
    }
    else if ([self.tempStr hasPrefix:@"0"] && [sender tag] == 0 && ![self.tempStr hasPrefix:@"0."])
    {
        //如果是以0开头,但是不是以0.开头,则直接返回
        return;
       
   }
    
    //处理小数点的问题
    //如果小数点是第一输入的数字
    if ([sender tag] == 10 && self.tempStr.length == 0)
    {
        self.tempStr = [NSMutableString stringWithString:@"0"];
    }
        //每输入一次,拼接一次字符串
    if([sender tag] == 10 )//取小数点
    {
        //小数点只允许输入一次
        //遍历字符串tempStr,如果有小数点,则直接return
        for (int i = 0; i < self.tempStr.length ; i++)
        {
            char c = [self.tempStr characterAtIndex:i];
            if (c == '.')
            {
                return;
            }
        }
         [self.tempStr appendString:@"."];
    }
    else
    {
         [self.tempStr appendFormat:@"%ld",[sender tag]];
    }
    _show.text = self.tempStr;
}
//删除按钮
-(IBAction)deleteNums:(id)sender
{
    if (_show.text.length == 1)//删除显示屏中所有的数字
    {
        _show.text = @"0";
        //清空tempStr
        self.tempStr = [NSMutableString stringWithString:@""];
        return;
    }
    //将显示屏中的现有数字赋值给字符串
//    NSMutableString *str = [[NSMutableString alloc]init];
    self.tempStr =[NSMutableString stringWithFormat:@"%@", _show.text] ;
    [self.tempStr deleteCharactersInRange:NSMakeRange(self.tempStr.length-1, 1)];
    _show.text = self.tempStr;
}
 
//监听加减乘除 calculate "=" 11    "+" 12      "-" 13    "*" 14    "/" 15  正负为16  %为17
-(IBAction)calculate:(id)sender
{
    //清空tempStr
    self.tempStr = [NSMutableString stringWithString:@""];
    if(0 == _count)//如果是第一次输入
    {
        _cal = [NSNumber numberWithLong:[sender tag]];
        self.num1 = [NSMutableString stringWithFormat:@"%@",_show.text];
    }
    else//不是第一次输入,则计算
    {
        self.num2 = [NSMutableString stringWithFormat:@"%@", _show.text];
        int calculate = [_cal intValue];
        switch (calculate) {
            case 12://将加后的结果显示
                _show.text =[NSString stringWithFormat:@"%.2f",([self.num1 doubleValue] + [self.num2 intValue])];
                break;
            case 13://将减后的结果显示
                _show.text =[NSString stringWithFormat:@"%.2f",([self.num1 doubleValue] - [self.num2 intValue])];
                break;
            case 14://将乘后的结果显示
                _show.text =[NSString stringWithFormat:@"%.2f",([self.num1 doubleValue] * [self.num2 intValue])];
                break;
            case 15://将除后的结果显示
                _show.text =[NSString stringWithFormat:@"%.2f",([self.num1 doubleValue] / [self.num2 intValue])];
                break;
            default:
                break;
        }
        self.num1 = [NSMutableString stringWithFormat:@"%@", _show.text];
        _cal = [NSNumber numberWithLong:[sender tag]];
    }
    _count = @1;
    if ([sender tag] == 16 || [sender tag] == 17)//单目运算正负和%
    {
        switch ([sender tag]) {
            case 16://将乘负后的结果显示
                _show.text =[NSString stringWithFormat:@"%.2f",([self.num1 doubleValue] *(-1))];
                break;
            case 17://将取百分后的结果显示
                _show.text =[NSString stringWithFormat:@"%.2f",([self.num1 doubleValue] / 100)];
                break;
            default:
                break;
        }
        self.num1 = [NSMutableString stringWithFormat:@"%@", _show.text];
    }
 
} 
