如何使 IEditableObject.EndEdit 原子化？

发布于 2024-07-06 11:18:22 字数 521 浏览 10 评论 0原文

如果我有一个实现 IEditableObject 的 Address 对象，我可能会有这样的 EndEdit 实现：

public void EndEdit()
{
    // BeginEdit would set _editInProgress and update *Editing fields;
    if (_editInProgress)
    {
        _line1 = _line1Editing;
        _line2 = _line2Editing;
        _city = _cityEditing;
        _state = _stateEditing;
        _postalCode = _postalCodeEditing;
        _editInProgress = false;
    }
}

例如，如果更新 _state 时出现异常，则所有 5 个属性都应重置。此原子更新问题可能不仅限于 EndEdit。

原文

If I have an Address object which implements IEditableObject, I might have EndEdit implementation like this:

public void EndEdit()
{
    // BeginEdit would set _editInProgress and update *Editing fields;
    if (_editInProgress)
    {
        _line1 = _line1Editing;
        _line2 = _line2Editing;
        _city = _cityEditing;
        _state = _stateEditing;
        _postalCode = _postalCodeEditing;
        _editInProgress = false;
    }
}

If there is an exception updating _state, for example, then all 5 properties should reset. This atomic update issue probably isn't limited to EndEdit.

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一百个冬季 2024-07-13 11:18:23

首先，肯特想知道为什么设置字段会引发异常是正确的。
忽略这个问题；您可以使用一个简单的方法：

try {
  //do stuff
}
catch (Exception ex) {
  //reset

  //rethrow exception
  throw;
}

复杂的问题是每个字段的重置值由什么构成？

最后一个值
默认值
一些表示无效状态的标记值
上述内容的混合

如果您需要“重置”到最后一个值，那么您可能需要某种方法来在对其执行某些操作之前轻松存储对象状态，以及如果出现问题，能够轻松恢复该状态。查看 Momento 模式处理这个问题的方法。

First off, Kent is correct in wondering why setting a field would throw an exception.
Ignoring that question; you could just use a simple:

try {
  //do stuff
}
catch (Exception ex) {
  //reset

  //rethrow exception
  throw;
}

The complications come in with regards to what constitutes the reset value for each field?

The last value
A default value
Some token value denoting an invalid state
A mix of the above

If you need to "reset" to the last value then you'll likely want some way to easily store the object state before doing something to it, along with the ability to easily restore that state should something go wrong. Check out the Momento Pattern on a nifty way to deal with that problem.

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雨的味道风的声音 2024-07-13 11:18:23

我不使用字段来存储值。相反，我使用属性可以读写的哈希表。这给了我一个非常简单的设计。

Friend Sub BeginEdit()
    m_Backup = New Dictionary(Of String, Object)(m_DataPoints, StringComparer.OrdinalIgnoreCase)
End Sub

Friend Sub CancelEdit()
    If m_Backup IsNot Nothing Then m_DataPoints = m_Backup
End Sub

Friend Sub EndEdit()
    m_Backup = Nothing
End Sub

I don't use fields for storing values. Instead I use a hash table that the properties can read and write. This gives me a really simple design.

Friend Sub BeginEdit()
    m_Backup = New Dictionary(Of String, Object)(m_DataPoints, StringComparer.OrdinalIgnoreCase)
End Sub

Friend Sub CancelEdit()
    If m_Backup IsNot Nothing Then m_DataPoints = m_Backup
End Sub

Friend Sub EndEdit()
    m_Backup = Nothing
End Sub

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