iphone - 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

你好!

我在 21.2 练习中遇到了麻烦。在该练习中，我构建了分数计算器。我有 9 个按钮和数学操作。当我在 iOS 模拟器上按任何数字(1、2、3 或任何其他数字)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 digital5]:无法识别的选择器发送到实例 0x6843e00””。

这是我的该程序的代码:

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

该错误消息意味着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 View Controller 类中定义它，可能与 digit0..digit9 方法一起定义。

不过，拥有十个方法可能不是最理想的:更好的方法是使用与各自数字相对应的标签来标记按钮，对所有数字按钮使用相同的方法，并在调用中获取标签。

tag是UIView的一个NSInteger属性，定义如下:

@property(nonatomic) NSInteger tag