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我不知道为什么排序不起作用NSArray。DBMetadata (NSObject)这是我的代码。怎么了？我什至尝试添加要添加的类别，compare:但它不起作用。

- (void)restClient:(DBRestClient *)client loadedMetadata:(DBMetadata *)metadata {
    if (metadata.isDirectory) {
        NSLog(@"Folder '%@' contains:", metadata.path);
        for (DBMetadata *file in metadata.contents) {
            NSLog(@"\t%@  is directory? %d", file.filename, file.isDirectory);
            if (file.isDirectory) {
                [self.availableBackups addObject:file];
                DLog(@"llastModifiedDate %@", file.lastModifiedDate);
            }
        }
    }
//    NSLog(@"before sorting: %@", self.availableBackups); //lastModifiedDate //filename

    NSSortDescriptor *descriptor = [[NSSortDescriptor alloc] initWithKey:@"lastModifiedDate"  ascending:YES selector:@selector(compare:)];
    [self.availableBackups sortedArrayUsingDescriptors:[NSArray arrayWithObjects:descriptor,nil]];

//    NSLog(@"after sorting: %@", self.availableBackups);
}

self.availableBackups是NSMutableArray

@property (nonatomic, retain) NSMutableArray *availableBackups;

Dropbox - DBMetadata.h

注释NSLog刚刚打印了obj的地址，可以看到无论YESor NOfor ，排序后输出的address都是一样的ascending:

输出

2013-01-31 17:20:12.423 Dropbox[7366:c07] before sorting: (
    "<DBMetadata: 0x6bbf010>",
    "<DBMetadata: 0x6bbfb50>",
    "<DBMetadata: 0x6bc1660>",
    "<DBMetadata: 0x6bc17b0>",
    "<DBMetadata: 0x6bc14f0>",
    "<DBMetadata: 0x6bc0dd0>",
    "<DBMetadata: 0x6bc1de0>"
)
2013-01-31 17:20:12.424 Dropbox[7366:c07] after sorting: (
    "<DBMetadata: 0x6bbf010>",
    "<DBMetadata: 0x6bbfb50>",
    "<DBMetadata: 0x6bc1660>",
    "<DBMetadata: 0x6bc17b0>",
    "<DBMetadata: 0x6bc14f0>",
    "<DBMetadata: 0x6bc0dd0>",
    "<DBMetadata: 0x6bc1de0>"
)

随着上升NO

Last Modified file at 0: 2013-01-30 08:00:22 +0000
Last Modified file at 1: 2013-01-30 08:02:54 +0000
Last Modified file at 2: 2013-01-31 09:08:26 +0000
Last Modified file at 3: 2013-01-31 09:14:55 +0000
Last Modified file at 4: 2013-01-31 09:14:08 +0000
Last Modified file at 5: 2013-01-31 09:16:43 +0000
Last Modified file at 6: 2013-01-31 10:36:13 +0000
4

1 回答 1

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sortedArrayUsingDescriptors:返回一个数组，它不会修改您正在应用它的数组。如果您需要使用NSArray，请尝试：

self.availableBackups = [self.availableBackups sortedArrayUsingDescriptors:[NSArray arrayWithObjects:descriptor,nil]];

如果你可以使用NSMutableArray，你可以使用：

[self.availableBackups sortUsingDescriptors:[NSArray arrayWithObjects:descriptor,nil]];
于 2013-01-31T11:52:40.363 回答