在计算器中追加或添加小数点功能

Question

我正在尝试将点功能添加到我的计算器中，但我一直在努力让它工作。

到目前为止，它所做的是添加小数点，但是当我按下另一个数字时，它所做的就是添加 0，而不管你按下的数字是什么......

示例：用户输入 9（点运算/十进制）然后 5 = 到 9.0

这当然是完全错误的。

最后，我专门发布了点函数和数字 9，它们是产生该答案的函数。

头文件..

int Method;
float SelectNumber;
float RunningTotal;
bool DecimalActived;

@interface ViewController : UIViewController{
    IBOutlet UILabel *Screen;
}

-(IBAction)Number9:(UIButton *)sender;
-(IBAction)Dot:(UIButton *)sender;  

@end

实施文件..（已更新）

-(IBAction)Number9:(UIButton *)sender{

    [self appendDigit:@"9"];

}

- (IBAction)Dot:(UIButton *)sender {

    NSString *currentText = Screen.text;
    if ([currentText rangeOfString:@"." options:NSBackwardsSearch].length == 0) {
        [self appendDigit:@"."];
    }

}

- (void)appendDigit:(NSString *)digit {
    // handle two special cases: append to only zero means just replace
    // but append decimal point to zero is a regular append
    if ([self->Screen.text isEqualToString:@"0"] && ![digit isEqual:@"."]) {
        self->Screen.text = digit;
    } else {
        self->Screen.text = [Screen.text stringByAppendingString:digit];
    }
}

计算（更新）

- (IBAction)Percent:(UIButton *)sender {

    [self MySwitch];

    Method = 5;
    SelectNumber = 0;
    DecimalActived = FALSE;
    Screen.text = [NSString stringWithFormat:@"%.2g", RunningTotal];

}


- (IBAction)PositiveOrNegative:(UIButton *)sender {

    [self MySwitch];

    Method = 6;
    SelectNumber = 0;
    DecimalActived = FALSE;
    Screen.text = [NSString stringWithFormat:@"%g", RunningTotal];

}


-(IBAction)Equals:(UIButton *)sender{

    [self MySwitch];

    Method = 0;
    SelectNumber = 0;
    DecimalActived = FALSE;
    Screen.text = [NSString stringWithFormat:@"%g", RunningTotal];

}


-(IBAction)AllClear:(UIButton *)sender{

    Method = 0;
    RunningTotal = 0;
    SelectNumber = 0;

    Screen.text = [NSString stringWithFormat:@"0"];

}

- (double) MySwitch {

     SelectNumber = [[NSNumberFormatter alloc] init];
     [SelectNumber setNumberStyle:NSNumberFormatterDecimalStyle];
     RunningTotal = [SelectNumber numberFromString:self->Screen.text];

     if (RunningTotal == 0) {
         RunningTotal = SelectNumber;
     } else{
        switch (Method) {
            case 1:
                RunningTotal = RunningTotal * SelectNumber;
                break;
            case 2:
                RunningTotal = RunningTotal / SelectNumber;
                break;
            case 3:
                RunningTotal = RunningTotal - SelectNumber;
                break;
            case 4:
                RunningTotal = RunningTotal + SelectNumber;
                break;
            case 5:
                RunningTotal = RunningTotal / 100;
                break;
            case 6:
                if(RunningTotal > 0){
                    RunningTotal = - RunningTotal;
                } else{
                    RunningTotal = + RunningTotal;
                }
                break;
            default:
                break;
        }
     }

    return RunningTotal;
}

如果你们需要更多对代码的参考，请告诉我，我们会提供它，或者在这方面有任何帮助的问题也请告诉我，我会提供信息:)

Answer 1

通过认识到输入的数值在您必须进行计算之前并不重要，可以简化问题。您可以让按钮和文本字段只关注文本行为，然后在需要时随时提取值。例如

// do this for digits and @"."
- (IBAction)button9:(id)sender {
    [self appendDigit:@"9"];
}

- (void)appendDigit:(NSString *)digit {
    // handle two special cases: append to only zero means just replace
    // but append decimal point to zero is a regular append
    if ([self.myTextField.text isEqualToString:@"0"] && ![digit isEqualToString:@"."]) {
        self.myTextField.text = digit;
    } else {
        self.myTextField.text = [myTextField.text stringByAppendingString:digit];
    }
}

// negative sign is special too...
self.myTextField.text = [@"-" stringByAppendingString:myTextField.text];

然后，只有稍后，当你需要进行计算时，你才能得到这样的数值：

NSNumberFormatter *f = [[NSNumberFormatter alloc] init];
[f setNumberStyle:NSNumberFormatterDecimalStyle];
NSNumber *number = [f numberFromString:self.myTextField.text];

最后，另一个很好的表示模式是将数值状态保持为 NSNumbers，在需要数学时转换为标量类型...

NSNumber *runningTotal;
NSNumber *currentValue;

// say the current operation is multiplication
float runningTotalFloat = [runningTotal floatValue];
float currentValueFloat = [currentValue floatValue];
float newRunningTotal = runningTotalFloat * currentValueFloat;

runningTotal = [NSNumber numberWithFloat: newRunningTotal];

Answer 2

您应该让用户将号码输入NSMutableString，我们称之为buffer。

- (void)appendCharacter:(char)c
{
    if(isdigit(c)) {
        [buffer appendFormat:@"%c", c];
    } else if(c == '.') {
        if([buffer rangeOfString:@"."].location != NSNotFound) {
            // user tried to add more than 1 decimal point
            BEEP();
        } else {
            [buffer appendString:@"."];
        }
    } else {
        // user writes some other character.
        // do whatever you like
    }
}

要获取浮点值，可以在缓冲区上调用 -floatValue。