我正在编写我的第一个 iPhone 应用程序之一 - 一种简单的方式来记住有关人的事情。我正在关注名为“iOS的基于文档的应用程序编程指南”的 iOS 文档,并且我已经到了查询本地设备和 iCloud 以检测和加载文档的地步。在指南中,他们使用了一个自定义类,并且由于他们没有显示该类的代码,我对它应该是什么样子感到困惑。他们给出了自定义类“FileRepresentation”的描述:
示例应用程序现在有一个自定义模型对象数组 (_fileList),其中封装了每个应用程序文档的名称和文件 URL。(FileRepresentation 是这些对象的自定义类。)
谁能举例说明“FileRepresentation”的类实现是什么样的?
部分是“管理文档的生命周期”页面上的清单4-3和4-4 :
清单 4-3
-(void)viewDidLoad {
[super viewDidLoad];
// set up Add and Edit navigation items here....
if (self.documentsInCloud) {
_query = [[NSMetadataQuery alloc] init];
[_query setSearchScopes:[NSArray arrayWithObjects:NSMetadataQueryUbiquitousDocumentsScope, nil]];
[_query setPredicate:[NSPredicate predicateWithFormat:@"%K LIKE '*.txt'", NSMetadataItemFSNameKey]];
NSNotificationCenter* notificationCenter = [NSNotificationCenter defaultCenter];
[notificationCenter addObserver:self selector:@selector(fileListReceived)
name:NSMetadataQueryDidFinishGatheringNotification object:nil];
[notificationCenter addObserver:self selector:@selector(fileListReceived)
name:NSMetadataQueryDidUpdateNotification object:nil];
[_query startQuery];
} else {
NSArray* localDocuments = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:
[self.documentsDir path] error:nil];
for (NSString* document in localDocuments) {
[_fileList addObject:[[[FileRepresentation alloc] initWithFileName:[document lastPathComponent]
url:[NSURL fileURLWithPath:[[self.documentsDir path]
stringByAppendingPathComponent:document]]] autorelease]];
}
}
}
清单 4-4
-(void)fileListReceived {
NSString* selectedFileName=nil;
NSInteger newSelectionRow = [self.tableView indexPathForSelectedRow].row;
if (newSelectionRow != NSNotFound) {
selectedFileName = [[_fileList objectAtIndex:newSelectionRow] fileName];
}
[_fileList removeAllObjects];
NSArray* queryResults = [_query results];
for (NSMetadataItem* result in queryResults) {
NSString* fileName = [result valueForAttribute:NSMetadataItemFSNameKey];
if (selectedFileName && [selectedFileName isEqualToString:fileName]) {
newSelectionRow = [_fileList count];
}
[_fileList addObject:[[[FileRepresentation alloc] initWithFileName:fileName
url:[result valueForAttribute:NSMetadataItemURLKey]] autorelease]];
}
[self.tableView reloadData];
if (newSelectionRow != NSNotFound) {
NSIndexPath* selectionPath = [NSIndexPath indexPathForRow:newSelectionRow inSection:0];
[self.tableView selectRowAtIndexPath:selectionPath animated:NO scrollPosition:UITableViewScrollPositionNone];
}
}