我不完全确定为什么它在注释行返回错误“不是 Objective-C 对象”。任何帮助,将不胜感激。
此外,我对 Objective-C 非常陌生,我确实意识到这很有可能是一个非常愚蠢的错误。但是,任何建议都会有所帮助。
#import "CalculatorBrain.h"
@interface CalculatorBrain()
@property (nonatomic, strong) NSMutableArray *operandStack;
@end
@implementation CalculatorBrain
@synthesize operandStack = _operandStack;
- (NSMutableArray *)operandStack
{
if(!_operandStack){
_operandStack = [[NSMutableArray alloc] init];
}// end if
return _operandStack;
}//end operandStack
- (void)pushOperand:(double)operand
{
NSNumber *operandObject = [NSNumber numberWithDouble:operand];
[self.operandStack addObject:operandObject];
}//end pushOperand
- (double)popOperand
{
NSNumber *operandObject = [self.operandStack lastObject];//error "Not an objective-c object"
if(operandObject) [self.operandStack removeLastObject];
return [operandObject doubleValue];
}//end popOperand
- (double)performOperation:(NSString *)operation
{
double result = 0;
if([operation isEqualToString:@"+"]){
result = [self popOperand] + [self popOperand];
} else if([operation isEqualToString:@"-"]){
double subtrahend = [self popOperand];
result = [self popOperand] - subtrahend;
} else if([operation isEqualToString:@"*"]){
result = [self popOperand] * [self popOperand];
} else if([operation isEqualToString:@"/"]){
double divisor = [self popOperand];
if(divisor) result = [self popOperand] / divisor;
}//end if
[self pushOperand:result];
return result;
}//performOperation
@end