新手求助！iOS建议计算器【unrecognized selector sent to instance】

Question

纠结好久不知道哪里错了！！请各位大神看看！！多谢~~~
CalculatorBrain.h#import <Foundation/Foundation.h>
@interface CalculatorBrain : NSObject
-(void)pushOperand:(double)operand;
-(double)performOperation:(NSString *)operation;
@end
CalculatorBrain.m
#import "CalculatorBrain.h"
@interface CalculatorBrain()
@property (nonatomic,strong)NSMutableArray *operandStack;
-(double)popOperand;
@end
@implementation CalculatorBrain
@synthesize operandStack = _operandStack;
-(void)pushOperand:(double)operand{
    NSNumber *operandObject = [NSNumber numberWithDouble:operand];
    [self.operandStack addObject:operandObject];
}
-(double)popOperand{
    NSNumber *operandObject = [self.operandStack lastObject];
    if(operandObject != nil) [self.operandStack removeLastObject];
    return [operandObject doubleValue];
}-(double)performOperation:(NSString *)operation{
    double result = 0;
    if([operation isEqualToString:@"+"]){
        result = [self popOperand] +[self popOperand];
    }
    else if([operation isEqualToString:@"-"]){
        result = [self popOperand] + [self popOperand];
    }
    else if([operation isEqualToString:@"*"]){
        result = [self popOperand] * [self popOperand];
    }
    else if([operation isEqualToString:@"/"]){
        result = [self popOperand] / [self popOperand];
    }
    [self pushOperand:result];
    return result;
}
-(void)setOperandStack:(NSMutableArray *)operandStack{
    _operandStack = operandStack;
}
-(NSMutableArray *)operandStack{
    if(_operandStack == nil){
        _operandStack = [[NSMutableArray alloc] init];
    }
    return _operandStack;
}
@end
XYZViewController.h
#import <UIKit/UIKit.h>
#import "CalculatorBrain.h"
@interface XYZViewController : UIViewController
@property (nonatomic) BOOL userIsInTheMiddleOfEnteringANumber;
@property (strong, nonatomic) IBOutlet UILabel *display;
@property (nonatomic,strong) CalculatorBrain *brain;
- (IBAction)digitPressed:(UIButton *)sender;
- (IBAction)operatorPressed:(UIButton *)sender;
- (IBAction)enterPressed;
@endXYZViewController.m
#import "XYZViewController.h"
#import "CalculatorBrain.h"
@implementation XYZViewController
@synthesize display = _display;
@synthesize userIsInTheMiddleOfEnteringANumber = _userIsInTheMiddleOfEnteringANumber;
@synthesize brain = _brian;
-(CalculatorBrain *)brain{
    if(!_brian){
        _brian = [[CalculatorBrain alloc] init];
    }
    return _brian;
}
- (IBAction)digitPressed:(UIButton *)sender {
    NSString *num = [sender currentTitle];
    if(self.userIsInTheMiddleOfEnteringANumber){
        UILabel *myDisplay = self.display;
        NSString *currentText = myDisplay.text;
        NSString *newText = [currentText stringByAppendingString:num];
        [myDisplay setText:newText];
    }else{
        UILabel *myDisplay = self.display;
        [myDisplay setText:num];
        self.userIsInTheMiddleOfEnteringANumber = YES;
    }
}
- (IBAction)operatorPressed:(UIButton *)sender {
    if(self.userIsInTheMiddleOfEnteringANumber) [self enterPressed];
    double result = [self.brain performOperation:[sender currentTitle]];
    self.display.text = [NSString stringWithFormat:@"%g",result];
}
- (IBAction)enterPressed{
    [self.brain pushOperand:[self.display.text doubleValue]];
    self.userIsInTheMiddleOfEnteringANumber = NO;
}
@end
控制台输出：
2014-08-26 21:21:44.070 Calculator[3733:60b] -[XYZViewController enterPressed:]: unrecognized selector sent to instance 0x8f56ce0
2014-08-26 21:21:44.073 Calculator[3733:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[XYZViewController enterPressed:]: unrecognized selector sent to instance 0x8f56ce0'
*** First throw call stack:
(
0   CoreFoundation                      0x017ed1e4 __exceptionPreprocess + 180
1   libobjc.A.dylib                     0x0156c8e5 objc_exception_throw + 44
2   CoreFoundation                      0x0188a243 -[NSObject(NSObject) doesNotRecognizeSelector:] + 275
3   CoreFoundation                      0x017dd50b ___forwarding___ + 1019
4   CoreFoundation                      0x017dd0ee _CF_forwarding_prep_0 + 14
5   libobjc.A.dylib                     0x0157e880 -[NSObject performSelector:withObject:withObject:] + 77
6   UIKit                               0x0022e3b9 -[UIApplication sendAction:to:from:forEvent:] + 108
7   UIKit                               0x0022e345 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 61
8   UIKit                               0x0032fbd1 -[UIControl sendAction:to:forEvent:] + 66
9   UIKit                               0x0032ffc6 -[UIControl _sendActionsForEvents:withEvent:] + 577
10  UIKit                               0x0032f243 -[UIControl touchesEnded:withEvent:] + 641
11  UIKit                               0x0026dddd -[UIWindow _sendTouchesForEvent:] + 852
12  UIKit                               0x0026e9d1 -[UIWindow sendEvent:] + 1117
13  UIKit                               0x002405f2 -[UIApplication sendEvent:] + 242
14  UIKit                               0x0022a353 _UIApplicationHandleEventQueue + 11455
15  CoreFoundation                      0x0177677f __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
16  CoreFoundation                      0x0177610b __CFRunLoopDoSources0 + 235
17  CoreFoundation                      0x017931ae __CFRunLoopRun + 910
18  CoreFoundation                      0x017929d3 CFRunLoopRunSpecific + 467
19  CoreFoundation                      0x017927eb CFRunLoopRunInMode + 123
20  GraphicsServices                    0x037e15ee GSEventRunModal + 192
21  GraphicsServices                    0x037e142b GSEventRun + 104
22  UIKit                               0x0022cf9b UIApplicationMain + 1225
23  Calculator                          0x00002c8d main + 141
24  libdyld.dylib                       0x01e34701 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

报错的位置在这里
[XYZViewController enterPressed:]
发送的是带参数的enterPressed：消息
而你在controller中定义的IBAction 如下
- (IBAction)enterPressed;  ///////无参
所以调用时因找不到带参数的enterPressed方法而报错修改controller的enterPressed的声明及实现 
////////头文件 .h
- (IBAction)enterPressed:(id)sender;
//////实现文件 .m
- (IBAction)enterPressed:(id)sender {
      //////////......to do your logic
}