添加NSDecimalNumbers不太起作用

Question

我有以下代码：

NSLog(@"Count of items we will loop through is: %d",[self.defaultBudgetItemsArray count]);
id object;
while (object = [e nextObject]) {
    if ([object objectForKey:@"actualCost"]) {
        currentTotal = [currentTotal decimalNumberByAdding: [object objectForKey:@"actualCost"]];
        NSLog(@"decimalNumberByAdding gives: %@",[numberFormatter stringFromNumber:[currentTotal decimalNumberByAdding: [object objectForKey:@"actualCost"]]]);
        NSLog(@"Trying to add: %@",[numberFormatter stringFromNumber:[object objectForKey:@"actualCost"]]);
    }
}

totalActualCostLabel.text = [numberFormatter stringFromNumber:currentTotal];
NSLog(@"Budget items total: %@",[numberFormatter stringFromNumber:currentTotal]);

控制台输出为：

2010-10-09 12:58:45.285 App[11659:307] Count of items we will loop through is: 6
2010-10-09 12:58:45.287 App[11659:307] decimalNumberByAdding gives: ($0.00)
2010-10-09 12:58:45.289 App[11659:307] Trying to add: $0.00
2010-10-09 12:58:45.292 App[11659:307] decimalNumberByAdding gives: ($0.00)
2010-10-09 12:58:45.293 App[11659:307] Trying to add: $0.00
2010-10-09 12:58:45.296 App[11659:307] decimalNumberByAdding gives: ($0.00)
2010-10-09 12:58:45.301 App[11659:307] Trying to add: $0.00
2010-10-09 12:58:45.303 App[11659:307] decimalNumberByAdding gives: ($0.00)
2010-10-09 12:58:45.305 App[11659:307] Trying to add: $5.00
2010-10-09 12:58:45.307 App[11659:307] decimalNumberByAdding gives: ($0.00)
2010-10-09 12:58:45.309 App[11659:307] Trying to add: $0.00
2010-10-09 12:58:45.311 App[11659:307] decimalNumberByAdding gives: ($0.00)
2010-10-09 12:58:45.318 App[11659:307] Trying to add: $0.00
2010-10-09 12:58:45.320 App[11659:307] Budget items total: ($0.00)

请注意，“尝试添加”行之一显示为$ 5.00，但decimalnumberbyadding似乎并未执行此操作。 有任何想法吗？

谢谢！

-最大

Answer 1

我们没有足够的信息来帮助您解决特定的问题。 也就是说，我尝试使用以下代码初始化您的代码：

NSArray *ary = [NSArray arrayWithObjects:
    [NSDictionary dictionaryWithObject:[NSDecimalNumber decimalNumberWithString:@"0"] forKey:@"actualCost"], 
    [NSDictionary dictionaryWithObject:[NSDecimalNumber decimalNumberWithString:@"4"] forKey:@"actualCost"], 
    [NSDictionary dictionaryWithObject:[NSDecimalNumber decimalNumberWithString:@"5"] forKey:@"actualCost"], 
    [NSDictionary dictionaryWithObject:[NSDecimalNumber decimalNumberWithString:@"2"] forKey:@"actualCost"], nil];

NSEnumerator *e = [ary objectEnumerator];
NSDecimalNumber *currentTotal = [NSDecimalNumber zero];
NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
[numberFormatter setNumberStyle:NSNumberFormatterCurrencyStyle];

上面的代码似乎没有任何问题，所以我不得不在@NSResponder的注释中第二次询问您的初始化代码。

另外，您的示例的以下行具有（我认为是）意外行为：

NSLog(@"decimalNumberByAdding gives: %@",[numberFormatter stringFromNumber:[currentTotal decimalNumberByAdding: [object objectForKey:@"actualCost"]]]);

这不会导致总数不正确，但是日志输出将产生误导。 机器到达该行时，它将已经添加了当前总和，并且您的日志将使它看起来好像已被添加了两次。 我认为您可能需要以下内容：

NSLog(@"decimalNumberByAdding gives: %@", [numberFormatter stringFromNumber:currentTotal]);

Answer 2

我最终接受了itaiferber的建议，即对所有内容都使用int并以美分为单位。 看起来很简单。 该代码最终显示为：

- (void)totalBudgetItems {
    NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
    [numberFormatter setFormatterBehavior:NSNumberFormatterBehavior10_4];
    [numberFormatter setCurrencySymbol:@"$"];
    [numberFormatter setNumberStyle:NSNumberFormatterCurrencyStyle];
    NSInteger currentTotal = 0;
    NSEnumerator *e = [self.defaultBudgetItemsArray objectEnumerator];
    NSLog(@"Count of items we will loop through is: %d",[self.defaultBudgetItemsArray count]);
    id object;
    while (object = [e nextObject]) {
        if ([object objectForKey:@"actualCost"]) {
            currentTotal = currentTotal + [[object objectForKey:@"actualCost"] intValue];
        }
    }
    NSNumber *tempDisplayTotalNumber = [NSNumber numberWithInt:currentTotal];
    totalActualCostLabel.text = [numberFormatter stringFromNumber:tempDisplayTotalNumber];
}

谢谢！！