Question

如何在应用程序启动时创建一个sqlite文件（didFinishLaunchingWithOptions）测试是否已经存在excist否则创建文件sqlite

Answer 1

像这样...... sqlPath变量是你资源上预先制作的sql数据库的路径

- (void) checkAndCreateSQL
{
    if (![[NSFileManager defaultManager] fileExistsAtPath:[documentPath stringByAppendingString:@"/database.sql"]]) {
        [[NSFileManager defaultManager] createFileAtPath:[documentPath stringByAppendingString:@"/database.sql"] 
                                                contents:[NSData dataWithContentsOfFile:sqlPath]
                                              attributes:nil];
    }
}

编辑1：

您可以使用以下命令行在Mac上创建数据库：

sqlite3 database.sql < DATABASE_CREATION.txt

在DATABASE_CREATION.txt中，如下所示：

CREATE TABLE IF NOT EXISTS `group` (
  `id` integer PRIMARY KEY,
  `name` text,
  `position` integer
);

然后将database.sql文件直接放入项目资源中。（如图像）

Answer 2

您可能希望使用默认的Core Data库，而不是手动创建和处理单个sqlite文件。请查看官方Apple Core Data Programming Guide。它将自动处理应用程序中内部数据库的创建和更新。

Answer 3

sqlite3 *reference2Database() {
if (_database == nil) {
    // First, test for existence.
    NSError *error;
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *writableDBPath = [documentsDirectory stringByAppendingPathComponent:@"my.sqlite"];

    if ([fileManager fileExistsAtPath:writableDBPath] == NO) {
        // Database file doesnt exists. Copy the database at writable path (documents directory).
        NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"my.sqlite"];

        [fileManager removeItemAtPath:writableDBPath error:nil];

        BOOL databaseCopied = [fileManager copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error];
        if (!databaseCopied) {
            // Handle the error...
        }
    }else {
        // Open the database. The database was prepared outside the application.
        if (sqlite3_open([writableDBPath UTF8String], &_database) != SQLITE_OK) {
            // Even though the open failed, call close to properly clean up resources.
            sqlite3_close(_database);
            _database = nil;
            // Additional error handling, as appropriate...
        }
    }
}
return _database;
}

//示例用法。

-(void) someDatabaseFunction {
   sqlite3 *database = reference2Database();
   // Do something with "database"...
}

//关闭数据库。应用程序终止时应该调用它。

void closeDatabase() {
if (_database == nil) return;
// Close the database.
if (sqlite3_close(_database) != SQLITE_OK) {
    // Handle the error...
}
_database = nil;

}

注意：在文件的顶部，你应该有：static sqlite3 * _database = nil;

Answer 4

我使用Matteo Bertozzi's SQLite Wrapper使用以下代码创建我的sqlite数据库：

-(void)checkDatabase 
{
    if([[NSFileManager defaultManager] fileExistsAtPath:DBPATH] == NO)
    {
        sqlite = [[Sqlite alloc] init];

        if (![sqlite open:DBPATH]) return;

        [sqlite executeNonQuery:@"DROP TABLE yourtable"];
        [sqlite executeNonQuery:@"CREATE TABLE yourtable (record1 TEXT NOT NULL, 
                                                           record2 TEXT NOT NULL, 
                                                           record3 TEXT NOT NULL, 
                                                           record4 TEXT NOT NULL);"];

        NSArray *results = [sqlite executeQuery:@"SELECT * FROM yourtable;"];
        for (NSDictionary *dictionary in results) {

            for (NSString *key in [dictionary keyEnumerator])
                NSLog(@" - %@ %@", key, [dictionary objectForKey:key]);
        }

        [results release];
        [sqlite release];
    }
}

如何创建一个sqlite

4 个答案: