当我按下计算器中的任何数字按钮时，iOS模拟器会生成错误

Question

您好！ 的

我在练习21.2时遇到麻烦。在那个练习中，我构建了Fraction计算器。我有9个按钮和数学动作。当我在iOS模拟器上按任意数字（1,2,3或其他任何数字）时，它会生成错误：

    2012-08-05 15:09:05.026 Fraction_Calculator[834:f803] -[ViewController digit5]: unrecognized selector sent to instance 0x6843e00
2012-08-05 15:09:05.029 Fraction_Calculator[834:f803] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[ViewController digit5]: unrecognized selector sent to instance 0x6843e00'
*** First throw call stack:
(0x14b5022 0xeb5cd6 0x14b6cbd 0x141bed0 0x141bcb2 0x14b6e99 0x1b14e 0x1b0e6 0xc1ade 0xc1fa7 0xc1266 0x403c0 0x405e6 0x26dc4 0x1a634 0x139fef5 0x1489195 0x13edff2 0x13ec8da 0x13ebd84 0x13ebc9b 0x139e7d8 0x139e88a 0x18626 0x28ad 0x2815)
terminate called throwing an exception

这意味着什么：“无法识别的选择器发送到实例0x6843e00 ”和“' - [ViewController digit5]：无法识别的选择器发送到实例0x6843e00'”强>”。

以下是该程序的代码：

ViewController.h

代码：Objective-C

#import <UIKit/UIKit.h>
#import "Calculator.h"

@interface ViewController : UIViewController

@property (strong, nonatomic) IBOutlet UILabel *display;

-(void) processDigit: (int) digit;
-(void) processOp: (char) theOp;
-(void) storeFracPart;

-(IBAction) clickDigit: (UIButton *) sender;

-(IBAction) clickPlus;
-(IBAction) clickMinus;
-(IBAction) clickMultiply;
-(IBAction) clickDivide;

-(IBAction) clickOver;
-(IBAction) clickEquals;
-(IBAction) clickClear;

@end

ViewController.m

代码：Objective-C

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController
{
    char                op;
    int                 currentNumber;
    BOOL                firstOperand, isNumerator;
    Calculator          *myCalculator;
    NSMutableString     *displayString;
}

@synthesize display;

-(void) processDigit:(int)digit
{
    currentNumber=currentNumber*10+digit;

    [displayString appendString:[NSString stringWithFormat:@"%i", digit]];
    display.text=displayString;
}

-(IBAction) clickDigit:(UIButton *)sender
{
    int digit=sender.tag;

    [self processDigit: digit];
}

-(void) processOp: (char) theOp
{
    NSString *opStr;

    op=theOp;

    switch(theOp)
    {
            case '+':
                opStr=@"+";
                break;
            case '-':
                opStr=@"-";
                break;
            case '*':
                opStr=@"*";
                break;
            case '/':
                opStr=@"/";
                break;
    }

    [self storeFracPart];
    firstOperand=NO;
    isNumerator=YES;

    [displayString appendString: opStr];
    display.text=displayString;
}

-(void) storeFracPart
{
    if(firstOperand)
    {
       if(isNumerator)
       {
           myCalculator.operand1.numerator=currentNumber;
           myCalculator.operand1.denominator=1;
       }
        else
            myCalculator.operand1.denominator=currentNumber;
    }
    else if (isNumerator)
    {
        myCalculator.operand2.numerator=currentNumber;
        myCalculator.operand2.denominator=1;
    }
    else
    {
        myCalculator.operand2.denominator=currentNumber;
        firstOperand=YES;
    }
currentNumber=0;
}

-(IBAction) clickOver
{
    [self storeFracPart];
    isNumerator=NO;
    [displayString appendString: @"/"];
    display.text=displayString;
}

-(IBAction) clickPlus
{
    [self processOp: '+'];
}

-(IBAction) clickMinus
{
    [self processOp: '-'];
}

-(IBAction) clickMultiply
{
    [self processOp: '*'];
}

-(IBAction) clickDivide
{
    [self processOp: '/'];
}

-(IBAction) clickEquals
{
    if (firstOperand==NO)
    {
        [self storeFracPart];
        [myCalculator performOperation: op];

        [displayString appendString: @"="];
        [displayString appendString: [myCalculator.accumulator convertToString]];
        display.text=displayString;

        currentNumber=0;
        isNumerator=YES;
        firstOperand=YES;
        [displayString setString: @""];        
    }
}

-(IBAction) clickClear
{
    isNumerator=YES;
    firstOperand=YES;
    currentNumber=0;
    [myCalculator clear];

    [displayString setString:@""];
    display.text=displayString;
}

- (void)viewDidLoad
{
    //[super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    firstOperand=YES;
    isNumerator=YES;
    displayString=[NSMutableString stringWithCapacity:40];
    myCalculator=[[Calculator alloc]init];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

@end

非常感谢！

Answer 1

错误消息表示代码正在尝试在没有名为digit5的方法的对象上调用方法digit5。如果这是您的按钮正在调用的方法，则需要在视图控制器类中定义它，可能与digit0 .. digit9方法一起定义。

有十种方法可能不是最理想的：更好的方法是用对应于各自数字的标签标记按钮，对所有数字按钮使用相同的方法，并在调用中收集标记。

tag是NSInteger的{​​{1}}属性，定义如下：

UIView