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POCritique – OO Design Flaws
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copied!<p>Recently, I received some negative feedback about the design of a class that I had originally thought to be innovative. After reflection, however, I agree it is clearly more flawed than innovative.</p> <p>This post invited the community to join in the review and provide its thoughtful feedback on the design flaws and identify a fix. </p> <p><strong>Background and Details:</strong></p> <p>The class in question is a domain object that gets dual-use in the business layer and in the UI. (Sometimes it is necessary.) </p> <p>The class includes a Display() Property that returns UI-friendly string. The rationale for including this Property is a convenience for class consumers. In my specific use, it was easy to bind a collection of this object to a UI grid control on the Display() Property.</p> <p>Display is implemented through a delegate so consumers can swap in another delegate.</p> <p><strong>Implementation</strong>:</p> <pre><code>//Within the "Measure" class is a delegate for the Display() public delegate string DisplayDelegate(IMeasure Measure); private DisplayDelegate _displayDelegate; </code></pre> <p>...</p> <pre><code>//The class uses a Write-Only Property sets the Display() delegate. //Within the constructor (not shown here), I set a default Display delegate by //concatenating a few properties together in a UI-friendly display string. public DisplayDelegate Display { set { _displayDelegate = value; } } //Class consumers call "MeasureDisplay" for a public string MeasureDisplay { get { return _displayDelegate.Invoke(this); } } </code></pre> <p>The responses below address the question of what is wrong with the design and what could fix it.</p>

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