SQLite sqlite3_prepare_v2 没有错误但也不好

Question

嘿伙计们，我只是在玩 SQLite，所以这对我来说是新的。我有一个可以保存和查找人员数据的视图。保存功能和查找功能完美运行。现在，我有了一个带有 tableView 的新视图。我想获取联系人表中的所有人员并用它填充列表。

到目前为止，我已经得到：

-(void)viewWillAppear:(BOOL)animated {
    const char *dbpath = [databasePath UTF8String];
    sqlite3_stmt *statement;

    if (sqlite3_open(dbpath, &contactDB) == SQLITE_OK)
    {
        NSLog(@"Opened DB");
        NSString *querySQL = [NSString stringWithFormat:@"SELECT name FROM contacts"];

        const char *query_stmt = [querySQL UTF8String];
        NSLog(@"could not prepare statement: %s\n", sqlite3_errmsg(contactDB));

        if (sqlite3_prepare_v2(contactDB, query_stmt, -1, &statement, NULL) == SQLITE_OK)
        //if (sqlite3_step(query_stmt) == SQLITE_DONE)
        {
            //NSLog(@"SQLite OK");
            NSLog(@"SQLite ok");
            //if (sqlite3_step(statement) == SQLITE_ROW)
            //{
                while(sqlite3_step(statement) == SQLITE_ROW) {
                    NSLog(@"SQLite ROW");
                    NSString *person = [[NSString alloc] initWithUTF8String:(const char *) sqlite3_column_text(statement, 0)];
                    [personsList addObject:person];
                }
            //} else {
            //    NSLog(@"Emtpy list");
            //}
            sqlite3_finalize(statement);
        }
        sqlite3_close(contactDB);
    }
    NSLog(@"Calling reload");
    NSLog(@"%@", personsList);
    [tabelView reloadData];
}

这一切都在 viewWillAppear 中。当视图加载并完成时，日志显示： 2011-05-06 10:45:26.976 数据库[1412:207] 打开数据库

2011-05-06 10:45:26.978 数据库[1412:207] 无法准备语句：不错误

2011-05-06 10:45:26.979数据库[1412:207] 调用重新加载

2011-05-06 10:45:26.979 数据库[1412:207] (

)

所以看来该语句是不是错误，但 sqlite3_prepare_v2 毕竟不是 SQL_OK。有什么帮助吗？

编辑：在上一个视图中，创建人员的语句是： @"INSERT INTO CONTACTS (姓名、地址、电话) VALUES (\"%@\", \"%@\", \"%@ \")",name.text,address.text,phone.text];

找人语句为：@"SELECT address,phone FROM Contacts WHERE name=\"%@\"" , name.text];

这两个语句起作用并显示数据。

Answer 1

@joetjah我使用你的代码来获取结果并且工作正常

2011-05-06 16:03:00.076 SQLiteDemo[6454:207] Opened DB
2011-05-06 16:03:09.550 SQLiteDemo[6454:207] could not prepare statement: not an error
2011-05-06 16:03:24.685 SQLiteDemo[6454:207] SQLite ok
2011-05-06 16:03:26.229 SQLiteDemo[6454:207] SQLite ROW
2011-05-06 16:03:28.254 SQLiteDemo[6454:207] SQLite ROW
2011-05-06 16:03:34.461 SQLiteDemo[6454:207] Calling reload
2011-05-06 16:03:35.009 SQLiteDemo[6454:207] (
    rahul,
    sqlite
)


-(void)testFunction{
    const char *dbpath = [databasePath UTF8String];
    sqlite3_stmt *statement;
    sqlite3 *contactDB;
    NSMutableArray *personsList = [[NSMutableArray alloc ] initWithCapacity:0];
    if (sqlite3_open(dbpath, &contactDB) == SQLITE_OK)
    {
        NSLog(@"Opened DB");
        NSString *querySQL = [NSString stringWithFormat:@"SELECT name FROM contacts"];

        const char *query_stmt = [querySQL UTF8String];
        NSLog(@"could not prepare statement: %s\n", sqlite3_errmsg(contactDB));

        if (sqlite3_prepare_v2(contactDB, query_stmt, -1, &statement, NULL) == SQLITE_OK)
            //if (sqlite3_step(query_stmt) == SQLITE_DONE)
        {
            //NSLog(@"SQLite OK");
            NSLog(@"SQLite ok");
            //if (sqlite3_step(statement) == SQLITE_ROW)
            //{
            while(sqlite3_step(statement) == SQLITE_ROW) {
                NSLog(@"SQLite ROW");
                NSString *person = [[NSString alloc] initWithUTF8String:(const char *) sqlite3_column_text(statement, 0)];
                [personsList addObject:person];
            }
            //} else {
            //    NSLog(@"Emtpy list");
            //}
            sqlite3_finalize(statement);
        }
        sqlite3_close(contactDB);
    }
    NSLog(@"Calling reload");
    NSLog(@"%@", personsList);
    //[tabelView reloadData];
}

你可以比较代码，可能的失败点可能是
1]数据未正确保存，因此未获取任何内容。
2]databasePath被设置为空白（当你得到Open Db日志时我对此表示怀疑）

表联系人是使用“CREATE TABLE联系人（姓名文本，年龄整数）”创建的
尝试一次，让我知道它是否有效。

Answer 2

试试这个，

-(void)viewWillAppear:(BOOL)animated {

    // Override point for customization after app launch.
    // Setup some globals
    // Get the path to the documents directory and append the databaseName
    NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDir = [documentPaths objectAtIndex:0];
    databasePath = [documentsDir stringByAppendingPathComponent:@"contacts.db"];

    const char *dbpath = [databasePath UTF8String];
    sqlite3_stmt *statement;

    if (sqlite3_open(dbpath, &contactDB) == SQLITE_OK)
    {
        NSLog(@"Opened DB");
        NSString *querySQL = [NSString stringWithFormat:@"SELECT name FROM CONTACTS"];
        const char *query_stmt = [querySQL UTF8String];

        NSLog(@"could not prepare statement: %s\n", sqlite3_errmsg(contactDB));

        if (sqlite3_prepare_v2(contactDB, query_stmt, -1, &statement, NULL) == SQLITE_OK)
        {
            NSLog(@"SQLite ok");
                while(sqlite3_step(statement) == SQLITE_ROW) {
                    NSLog(@"SQLite ROW");
                    NSString *person = [[NSString alloc] initWithUTF8String:(const char *) sqlite3_column_text(statement, 0)];
                    [personsList addObject:person];
                }
            sqlite3_finalize(statement);
        }
        else
        {
            //NSLog(@"could not prepare statement: %s\n", sqlite3_errmsg(statement));
        }
        sqlite3_close(contactDB);
    }
    NSLog(@"Calling reload");
    NSLog(@"%@", personsList);
    [tabelView reloadData];
}

Answer 3

我使用了 const char *dbpath = [databasePath UTF8String];，但我忘记将以下代码放在上面：

// Get the documents directory
    NSString *docsDir;
    NSArray *dirPaths;
    dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    docsDir = [dirPaths objectAtIndex:0];
    databasePath = [[NSString alloc] initWithString: [docsDir stringByAppendingPathComponent: @"contacts.db"]];
    const char *dbpath = [databasePath UTF8String];

Answer 4

这对我有用：

在 didload 函数中创建表，然后添加它（假设您已经声明了其他表视图函数）：

public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell{
    let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! TableViewCell        

    var selectStatement: OpaquePointer? = nil
    let selectSql = "select * from Inventory where ID = \((indexPath.row + 1))"
    if sqlite3_prepare_v2(Database.database.sqliteDB, selectSql, -1, &selectStatement, nil) == SQLITE_OK{
        if sqlite3_step(selectStatement) == SQLITE_ROW {

            let nameItem = sqlite3_column_text(selectStatement, 1)
            let price = sqlite3_column_double(selectStatement, 2)
            let quantity = sqlite3_column_int(selectStatement, 3)

            let nameString = String(cString: nameItem!)
            let priceString = String(format: "%.1f",price)
            let quantityString = String(quantity)

            cell.itemName.text = nameString
            cell.itemPrice.text = priceString
            cell.itemQuantity.text = quantityString

        }
    }

    return cell
}