我是iOS
的全新品牌。
我在线观看斯坦福大学的视频,了解iOS
。我花了几个小时慢慢地仔细浏览第二个视频,确保我没有在一行代码上蠢蠢欲动。一切都很完美,直到 - 你不知道 - 最后一分钟的编码。
我和我的妻子花了很多时间试图解决这个问题,但我的代码与教授的最佳匹配。请帮我。我很喜欢通过这些视频学习,但我不能继续前进,直到我有这个功能,并花时间来审查它。
#import "CalculatorViewController.h"
#import "CalculatorBrain.h"
@interface CalculatorViewController()
@property (nonatomic) BOOL userIsInTheMiddleOfEnteringANumber;
@property (nonatomic, strong) CalculatorBrain *brain;
@end
@implementation CalculatorViewController
@synthesize display = _display;
@synthesize userIsInTheMiddleOfEnteringANumber =
_userIsInTheMiddleOfEnteringANumber;
@synthesize brain = _brain;
- (CalculatorBrain *)brain
{
if (!_brain) _brain = [[CalculatorBrain alloc] init];
return _brain;
}
- (IBAction)digitPressed:(UIButton *)sender
{
NSString *digit = sender.currentTitle;
if (self.userIsInTheMiddleOfEnteringANumber)
{
self.display.text = [self.display.text stringByAppendingString:digit];
}
else
{
self.display.text = digit;
self.userIsInTheMiddleOfEnteringANumber = YES;
}
}
- (IBAction)enterPressed
{
[self.brain pushOperand:[self.display.text doubleValue]];
self.userIsInTheMiddleOfEnteringANumber = NO;
}
- (IBAction)operationPressed:(id)sender
{
if (self.userIsInTheMiddleOfEnteringANumber) [self enterPressed];
double result = [self.brain performOperation:sender.currentTitle]; // <- HERE IS THE LINE IN QUESTION
NSString *resultString = [NSString stringWithFormat:@"%g", result];
self.display.text = resultString;
}
@end
CalculatorBrain.m
#import "CalculatorBrain.h"
@interface CalculatorBrain()
@property (nonatomic, strong) NSMutableArray *operandStack;
@end
@implementation CalculatorBrain
@synthesize operandStack = _operandStack;
- (NSMutableArray *) operandStack
{
if (_operandStack == nil) _operandStack = [[NSMutableArray alloc] init];
return _operandStack;
}
- (void)pushOperand:(double)operand
{
[self.operandStack addObject:[NSNumber numberWithDouble:operand]];
}
- (double)popOperand
{
NSNumber *operandObject = [self.operandStack lastObject];
if (operandObject) [self.operandStack removeLastObject];
return [operandObject doubleValue];
}
- (double)performOperation:(NSString *)operation
{
double result = 0;
if ([operation isEqualToString:@"+"])
{
result = [self popOperand] + [self popOperand];
}
else if ([@"*" isEqualToString:operation])
{
result = [self popOperand] * [self popOperand];
}
[self pushOperand:result];
return result;
}
@end
答案 0 :(得分:1)
我认为问题在于你的if语句没有正确关闭。
- (IBAction)operationPressed:(id)sender
{
if (self.userIsInTheMiddleOfEnteringANumber){ [self enterPressed];
double result = [self.brain performOperation:sender.currentTitle];
NSString *resultString = [NSString stringWithFormat:@"%g", result];
self.display.text = resultString;
}
}
或
- (IBAction)operationPressed:(id)sender
{
if (self.userIsInTheMiddleOfEnteringANumber)
{
[self enterPressed];
}
double result = [self.brain performOperation:sender.currentTitle];
NSString *resultString = [NSString stringWithFormat:@"%g", result];
self.display.text = resultString;
}
建议查看教程的pdf文件以获得更具体的代码源。希望有所帮助。