Type Checking for Class Row Factory

首先查看 Issue #42 和 PR #57，因为其中描述了所提议的解决方案。然后检查 comdb2.dataclasses.class_row_factory，并将 BaseRowFactoryClass 示例与所述的类型检查问题进行比较。完成的标准是确认 PR 是否完全解决了 dataclass 属性和数据库输出的验证问题。

As described in Issue #42 there was a proposed solution for having a Class Row Factory. Alongside the conversations happened there, there was a concern regarding type checking for the attributes of the class and output returned by the database. There doesn't seem to be a way to enforce type checking hence an extra __post_init__ method would be required within the class to enforce type checking. This can be overlooked by a lot of developers and can lead to a lot of type mismatches.

Solution

Define a Base class that our dataclasses can inherit. The Base class can have all the required methods for the validation etc.

The updated use of it can be described it here. The solution has been implemented on the PR #57

        >>> from dataclasses import dataclass
        >>> from comdb2.dataclasses.class_row_factory import BaseRowFactoryClass
        ...
        >>> @dataclass
        >>> class ABC(BaseRowFactoryClass):
        >>>     x: int
        >>>     y: int
        
        ...
        >>> conn.row_factory = ClassRowFactory(ABC)
        >>> row = conn.cursor().execute("select 1 as x, 2 as y").fetchone()
        >>> print(row)
        <>
        >>> print(row.x)