Question

        self.sections = [[NSMutableDictionary alloc] init];
        BOOL found;
        for (NSDictionary *wine in sortedWines)
        {
            NSNumber *rate = [wine valueForKey:@"Rate"];
            NSString *rateStr = [NSString stringWithFormat:@"%.f", [rate floatValue]];
            found = NO;
            for (NSString *str in [self.sections allKeys])
            {
                if ([str isEqualToString:rateStr])
                {
                    found = YES;
                }
            }
            if (!found)
            {[self.sections setValue:[[NSMutableArray alloc] init] forKey:rateStr];}
        }
        for (NSDictionary *wine in sortedWines)
        {[[self.sections objectForKey:[NSString stringWithFormat:@"%.f", [[wine valueForKey:@"Rate"] floatValue]] ] addObject:wine];}

        // Sort:
        for (NSString *key in [self.sections allKeys])
        {[[self.sections objectForKey:key] sortUsingDescriptors:[NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"Rate" ascending:NO]]];}

此代码将我的葡萄酒分成几部分，但不会按降序排序！可能是因为NSNumber转换为NSString？我试图使用NSNumber值创建代码：

        self.sections = [[NSMutableDictionary alloc] init];
        BOOL found;
        for (NSDictionary *wine in sortedWines)
        {
            NSNumber *rate = [wine valueForKey:@"Rate"];
            found = NO;
            for (NSNumber *str in [self.sections allKeys])
            {
                if ([str isEqualToNumber:rate])
                {
                    found = YES;
                }
            }
            if (!found)
            {[self.sections setValue:[[NSMutableArray alloc] init] forKey:rate];}
        }
        // Loop again to sort wines into their keys
        for (NSDictionary *wine in sortedWines)
        {[[self.sections objectForKey:[wine valueForKey:@"Rate"]] addObject:wine];}

        // Sort each section array
        for (NSString *key in [self.sections allKeys])
        {[[self.sections objectForKey:key] sortUsingDescriptors:[NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"Rate" ascending:NO]]];}

但它给出了

的警告

if (!found)
{[self.sections setValue:[[NSMutableArray alloc] init] forKey:rate];}

表示“不兼容的指针类型将NSNumber ___强发送到NSString类型的参数”

如果我运行该应用程序，则会因错误-[__NSCFNumber localizedCaseInsensitiveCompare:]: unrecognized selector sent to instance 0x1e085810

而崩溃

我需要更改什么才能使其工作并按降序对部分进行排序？感谢。

Answer 1

我不知道sortDescriptorWithKey的默认选择器：升序：现在是caseInsensitiveCompare：，我很确定它曾经只是比较：在任何情况下，您都可以使用sortDescriptorWithKey：ascending：selector：来代替，并为选择器传递compare :.我认为应该修复你的第二个错误。仍然不确定为什么你会收到第一个错误。

Answer 2

如果您将代码格式化为易读性，那么您会做得更好（我们会更好地理解您）。例如：

    // Loop again to sort wines into their keys
    for (NSDictionary *wine in sortedWines) {
        NSArray* section = [self.sections objectForKey:[wine valueForKey:@"Rate"]];
        [section addObject:wine];
    }

    // Sort each section array
    NSArray* sortDescriptorArray = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"Rate" ascending:NO]];
    for (NSString *key in [self.sections allKeys]) {
         NSArray* section = [self.sections objectForKey:key];
         [section sortUsingDescriptors:sortDescriptorArray];
    }

除此之外，这使得调试变得更加简单，因为您可以停止并转储section数组。

或者，如果你真的更喜欢它，那么我强烈建议你学习APL或LISP。

尝试按降序对部分进行排序

2 个答案: