我正在使用iOS 5为iPhone开发RPN计算器进行编程任务,但我不确定如何在Objective-C中创建一个堆栈来推动数字。我可以在这部分使用一些帮助,因为应用程序的其余部分运行良好。
-(NSMutableArray *)operandStack // override the getter for lazy instantiation
{
if (!_operandStack)
{
[self setOperandStack:[[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];
if (operandObject)
{
[[self operandStack] removeLastObject];
return [operandObject doubleValue];
}
else
{
return 0;
}
}