Question

我正在编写我的第一个iPhone应用程序 - 一种记住人物事物的简单方法。我正在关注名为“Document-Based App Programming Guide for iOS”的iOS文档，我已经到了查询本地设备和iCloud以检测和加载文档的位置。在指南中，他们使用自定义类，因为他们没有显示类的代码，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：

示例应用程序现在具有自定义模型的数组（_fileList）封装每个的名称和文件URL的对象申请文件。（FileRepresentation是自定义类那些对象。）

任何人都可以举例说明“FileRepresentation”的类实现是什么样的吗？

部分是“Managing the Lifecycle of a Document”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];
     }
 }

Answer 1

对于将来会看到这一点的人来说，这就是我通过了解其他类如何实现其init函数来解决的问题：

#import "FileRepresentation.h"

@implementation FileRepresentation

@synthesize fileName = _fileName, fileUrl=_fileUrl;

-(id) initWithFileName:(NSString*)fileName url:(NSURL*)url
{
    self = [super init];
    if(self){
        self.fileName = fileName;
    }
    return self;
}

@end

困惑于基于文档的iPhone应用程序指南

1 个答案: