ios 没有可见的界面错误
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原文地址: http://stackoverflow.com/questions/9574597/
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No visible interface error
提问by pdenlinger
I have an error in the implementation file for my model which I have commented out. What can I do to fix this problem?
我的模型的实现文件中有一个错误，我已经注释掉了。我能做些什么来解决这个问题？
Thanks in advance.
提前致谢。
#import "CalculatorBrain.h"
@interface CalculatorBrain()
@property (nonatomic, strong) NSMutableSet *operandStack;
@end
@implementation CalculatorBrain
@synthesize operandStack = _operandStack;
- (NSMutableArray *)operandStack
{
if (!_operandStack) {
_operandStack = [[NSMutableArray alloc] init];
}
return _operandStack;
}
-(void)pushOperand:(double)operand
{
NSNumber *operandObject = [NSNumber numberWithDouble:operand];
[self.operandStack addObject:operandObject];
}
- (double)popOperand
{
NSNumber *operandObject = [self.operandStack lastObject]; // No visible interface for 'NSMutableSet' declares the selector 'lastObject'
if(operandObject) [self.operandStack removeLastObject]; // No visible interface for 'NSMutableSet' declares the selector '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];
} else if ([operation isEqualToString:@"-"]) {
double subtrahend = [self popOperand];
result = [self popOperand] - subtrahend;
} else if ([operation isEqualToString:@"/"]) {
double divisor = [self popOperand];
if (divisor)result = [self popOperand] / divisor;
}
[self pushOperand:result];
return result;
}
@end
采纳答案by rob mayoff
You have declared your operandStackproperty as an NSMutableSet, but you should have declared it as an NSMutableArray:
您已将您的operandStack财产声明为NSMutableSet，但您应该将其声明为NSMutableArray：
@property (nonatomic, strong) NSMutableArray *operandStack;
回答by Alex Coplan
You are trying to get the "last object" of an NSSet- this is impossible, as sets are unordered. The method lastObjectdoes not exist for NSMutableSet.
您正在尝试获取 an 的“最后一个对象” NSSet- 这是不可能的，因为集合是无序的。lastObjectNSMutableSet 不存在该方法。
You might want to try using an NSMutableArray instead.
您可能想尝试使用 NSMutableArray 代替。
