Question

我正在尝试删除数据库中的所有行，因为我编写了以下代码..

- (id)init {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *databasePath = [documentsDirectory stringByAppendingPathComponent:@"dataBase.sqlite3"];
    bool databaseAlreadyExists = [[NSFileManager defaultManager] fileExistsAtPath:databasePath];
    if (!databaseAlreadyExists){
        NSString *databasePathFromApp = [[NSBundle mainBundle] pathForResource:@"dataBase" ofType:@"sqlite3"];
        [[NSFileManager defaultManager] copyItemAtPath:databasePathFromApp toPath:databasePath error:nil];
    }
    if (sqlite3_open([databasePath UTF8String], &_database) == SQLITE_OK){
    }
    return self;
}
-(void)deleteAll{
    NSString *query = @"DELETE FROM user_info";
    sqlite3_stmt *statement = nil;
    if (sqlite3_prepare_v2(_database, [query UTF8String], -1, &statement, nil) == SQLITE_OK) {
        NSLog(@"Should delete..");
    }
    sqlite3_finalize(statement);
    sqlite3_close(_database);
}

但是当我重建app时，数据会出现。我做错了什么？

Answer 1

尝试条件if：

if(sqlite3_prepare_v2(database, sql, -1, &deletestmt, NULL) != SQLITE_OK)

Answer 2

您永远不会致电sqlite3_step来实际执行查询。

此外，您在错误的位置关闭数据库。你的结束应该在开放的对面完成。

Answer 3

首先，在打开数据库之后获取数据库路径

NSString *dbPath1=[SqliteManager getDataBasePath];
if (sqlite3_open([dbPath1 UTF8String], &database) == SQLITE_OK)
{
    NSLog(@"opened the data base");
    const char *sql = "delete from travels";
if(sqlite3_prepare_v2(database, sql, -1, &deletestmt, NULL) == SQLITE_OK)
        if(SQLITE_DONE != sqlite3_step(deletestmt))
            NSAssert1(0, @"Error while deleting. '%s'", sqlite3_errmsg(database));
        else
            isdeleted=YES;
}
sqlite3_reset(deletestmt); 
sqlite3_close(database);

write in ur method inside..... 
Getting Database Path....
+(NSString *)getDataBasePath
 {  
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory , NSUserDomainMask, YES);
NSString *documentsDir = [paths objectAtIndex:0];
NSLog(@"file Path is %@",documentsDir);
return [documentsDir stringByAppendingPathComponent:@"Give ur Sqlite Filename"];    
}

ios- sqLite不删除行

3 个答案: