向iOS计算器添加小数点按钮

Question

我遵循了一个制作iOS计算器的教程，现在我想在其中添加一个小数点按钮。这是我的代码

头文件：

#import <UIKit/UIKit.h>
@interface CalcViewController : UIViewController {
float result;
float selectedNumber;
int selectedOperation;
IBOutlet UILabel *calcScreen;
}
-(IBAction)numberPressed:(id)sender;
-(IBAction)operationPressed:(id)sender;
-(IBAction)clearNumber:(id)sender;
-(IBAction)clearOperation:(id)sender;
@end

这是我的实现文件

#import "CalcViewController.h"
@implementation CalcViewController
-(IBAction)numberPressed:(id)sender {
selectedNumber = selectedNumber * 10 + (float) [sender tag];
calcScreen.text = [NSString stringWithFormat:@"%2g", selectedNumber];
}
-(IBAction)operationPressed:(id)sender {
if (selectedOperation == 0) {
    result = selectedNumber;
} else {
    switch (selectedOperation) {
        case 1:
            result = result + selectedNumber;
            break;
        case 2:
            result = result - selectedNumber;
            break;
        case 3:
            result = result * selectedNumber;
            break;
        case 4:
            result = result / selectedNumber;
            break;
        case 5:
            selectedOperation = 0;
            break;

    }
}
selectedNumber = 0; 
calcScreen.text = [NSString stringWithFormat:@"%2g", result];
if ([sender tag] == 0) result = 0;
selectedOperation = [sender tag];
} 

-(IBAction)clearNumber:(id)sender {
selectedNumber = 0;
calcScreen.text = @"0";
}
-(IBAction)clearOperation:(id)sender {
selectedNumber = 0;
calcScreen.text = @"0";
selectedOperation = 0;
}

我在另一个帖子上看到有人建议使用这种方法：

- (IBAction)Decimal:(id)sender 
{
 NSString *currentText = calcScreen.text;
 if ([currentText rangeOfString:@"." options:NSBackwardsSearch].length == 0) {
    calcScreen.text = [calcScreen.text stringByAppendingString:@"."];  
}

然而，这似乎对我不起作用。它确实可以让我输入一个小数点，但当输入第二个数字时，小数点就会丢失。有人能提出一个我可以实施的方法来实现我想要的目标吗？

提前干杯！

Answer 1

我的快速想法是：在屏幕上保持数字为文本，并将额外的数字和/或小数点添加为文本。只在执行操作的那一刻将其转换为浮点值（顺便说一句，我会使用double我自己）。然后，建议的方法应该可以正常工作。

类似于：

-(IBAction)numberPressed:(id)sender {
    calcScreen.text = [calcScreen.text stringByAppendingString:[sender tag]];
}
-(IBAction)operationPressed:(id)sender {
    selectedNumber = [calcScreen.text floatValue];
    ...
}

Answer 2

一个快速提示，而不是使用代码中的int selectedOperation;...及更高版本

switch (selectedOperation) {
    case 1:
        result = result + selectedNumber;
        break;
    case 2:
        result = result - selectedNumber;
    ...

尝试使用typedef enum

    typedef enum {
    OperationTypeAdd = 0,
    OperationTypeSub,
    ...
    } OperationType

并且在switch块中

    switch (operationType) {
    case OperationTypeAdd:
        result = result + selectedNumber;
        break;
    case operationTypeSub:
        result = result - selectedNumber;
        break;