从远程SQLite获取数据

Question

首先，我创建了“subjects.sqlite”并将其插入Xcode文件“Copy Bundle Resrources”

我使用了这段代码

NSData *fetchedData = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://www.precaliga.com/iphone/subjects.sqlite"]];
    NSString *documentsPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *filePath = [documentsPath stringByAppendingPathComponent:@"subjects.sqlite"];
    [fetchedData writeToFile:filePath atomically:YES];

    NSFileManager *fileMgr = [NSFileManager defaultManager];

    BOOL success = [fileMgr fileExistsAtPath:filePath];
    if (!success) {
        NSLog(@"Cannot locate database file '%@'.", filePath);
    }
    else {
        self.db = [DBController sharedDatabaseController:filePath];
        DataTable* table = [_db  ExecuteQuery:@"SELECT * FROM subjects"];
        NSLog(@"%@",table.columns);
        NSLog(@"Downloaded Successfuly ..");
    }

但是“table.columns”返回

2013-04-12 11：34：06.202 Precaliga [82123：c07]（ ）

因为它没有读取下载的sqlite文件。所以我怎样才能在下载功能后读取数据

提前致谢..请帮帮我

Answer 1

试试这个

NSData *fetchedData = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://www.precaliga.com/iphone/subjects.sqlite"]];
NSLog(@"%d",fetchedData.length);
NSString *documentsPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *filePath = [documentsPath stringByAppendingPathComponent:@"subjects.sqlite"];
if (![[NSFileManager defaultManager] fileExistsAtPath:filePath])
     [[NSFileManager defaultManager] createFileAtPath:filePath contents:fetchedData attributes:nil];
[fetchedData writeToFile:filePath atomically:YES];

NSFileManager *fileMgr = [NSFileManager defaultManager];

BOOL success = [fileMgr fileExistsAtPath:filePath];
if (!success)
{
    NSLog(@"Cannot locate database file '%@'.", filePath);
}
else
{
    NSLog(@"Downloaded Successfuly ..");
}

修改

在AppDelegate.m

中写下这些内容

- (void) copyDatabaseIfNeeded
{
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSError *error;
    NSString *folderPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES) objectAtIndex:0];
    // First, test for existence.
    if (![fileManager fileExistsAtPath:folderPath])
        [fileManager createDirectoryAtPath:folderPath withIntermediateDirectories:YES attributes:nil error:&error]; //Create folder

    NSString *dbPath = [folderPath stringByAppendingPathComponent:@"subjects.sqlite"];
    BOOL success = [fileManager fileExistsAtPath:dbPath];

    if(!success)
    {
        NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"subjects.sqlite"];
        success = [fileManager copyItemAtPath:defaultDBPath toPath:dbPath error:&error];
        if (!success)
            NSAssert1(0, @"subjects.sqlite : Failed to create writable database file with message '%@'.", [error localizedDescription]);
    }
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    /** Database copy is not exist **/
    [self copyDatabaseIfNeeded]; // Call this way
}