Question

我想在应用程序启动时确保在UIDocument openWithCompletionHandler：完成之前不会发生任何事情。事情是openWithCompletionHandler在主线程上运行，我相信它必须（？）

我目前正在使用异步方法，但它是竞争条件，有时核心数据有时不会在我的rootViewController加载时初始化

- (void)useDocument {
    [self setPersistentStoreOptionsInDocument:self.document];

    if(![[NSFileManager defaultManager] fileExistsAtPath:[self.document.fileURL path]]) {
        [self.document saveToURL:self.document.fileURL forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) {
            self.isReady = YES;
            self.success = success;
        }];
    } else if (self.document.documentState == UIDocumentStateClosed) {
        [self.document openWithCompletionHandler:^(BOOL success) {
            self.isReady = YES;
            self.success = success;
        }];
    } else if (self.document.documentState == UIDocumentStateNormal) {
        self.isReady = YES;
        self.success = YES;
    }
}

提前谢谢

Answer 1

这是一个有效的示例代码，严格来说，您可能必须实现其他一些机制： 1.添加时钟或 maxTimes 以限制迭代。

在第一次使用之前检查 managedObjectContext 是否为零，对于YES，请将UIDocumentState检查为：
更多***应考虑UIDocumentState ***，其中包括：

UIDocumentStateClosed （尚未完成打开/创建，只需稍等片刻再试一次） UIDocumentStateSavingError （在完成处理程序中成功为NO） UIDocumentStateEditingDisabled （时效情况，请重试） UIDocumentStateInConflict （例如，因为其他一些人通过iCloud更改了它）

//header file
@interface file2CoredataClass : NSObject{

}
-(void)manualSave;
-(void)manualClose;
-(void)addAllPaths;
@property NSManagedObjectContext *managedObjectContext;
@end

//implementation
@implementation file2CoredataClass
UIManagedDocument *doc;
NSFileManager *fm;
-(id)init{
    self=[super init];
    if(self){
        fm = [NSFileManager defaultManager];
        NSURL *docDirectory = [[fm URLsForDirectory:NSDocumentationDirectory inDomains:NSUserDomainMask] firstObject];
        //notice:for some reason i don't know, the directory may not exist, and you can never create a document in this situation.
        //so, check if directory exists, and if not, create the directory.
        if(![fm fileExistsAtPath:[NSString stringWithFormat:@"%@",docDirectory] isDirectory:&isDir]){
            [fm createDirectoryAtPath:[NSString stringWithFormat:@"%@",docDirectory]  withIntermediateDirectories:YES attributes:nil error:nil];
        }
        NSString *docName = @"geoDoc";
        NSURL *url = [docDirectory URLByAppendingPathComponent:docName];
        doc = [[UIManagedDocument alloc]initWithFileURL:url]; // this creates the UIManagedDocument but not yet open or create the underlying file.
        //open or create the file
        [self openCreateFile:fm documentURL:url];

    }
    return self;
}

-(void)openCreateFile:(NSFileManager *)fm documentURL:(NSURL *)url{
    BOOL fileExists = [fm fileExistsAtPath:[url path]];
    if(fileExists){
        [doc openWithCompletionHandler:^(BOOL success) {
            //block to execute as file operation is asynchronous
            if(!success){
                [self openCreateFile:fm documentURL:url];
            }else if(doc.documentState == UIDocumentStateNormal){
                _managedObjectContext = doc.managedObjectContext;
            }
        }];
    }else{
        [doc saveToURL:url forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) {
            //block to execute as file operation is asynchronous
            if(!success){
                [self openCreateFile:fm documentURL:url];
            }else if(doc.documentState == UIDocumentStateNormal){
                _managedObjectContext = doc.managedObjectContext;
            }
        }];
    }
}
@end

如何等待UIDocument openWithCompletionHandler执行？

1 个答案: