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POInteresting API Design/Pattern
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copied!<p>I am re-designing part of our internal ORM tool, and I want to expose Field (a class that represents a field in the database, like CustomerFirstName) directly to the end-developer.</p> <p>So that was easy enough to accomplish, however the API got a little ugly because this Field class was previously used internally and is too open. For instance, and this is just one small example: the IsDirty property was not read-only, and that's something end-developers shouldn't be able to tamper with.</p> <p>I thought about maybe creating two interfaces, IPublicField and IPrivateField, and trying to get the field class to implement both of them. However, continuing with the IsDirty example, I didn't want something like this:</p> <pre><code>Public ReadOnly Property PrivateIsDirty Implements IPrivateField.IsDirty ... End Property Public Property IsDirty Implements IPublicField.IsDirty ... End Property </code></pre> <p>...It's just a little ugly, plus you could still cast back to the Field class and get into the non-readonly method. I also didn't want to introduce a seperate setter method because it would be another breaking change that I don't want to think about, and it also would create an inconsistency with other parts of the API.</p> <p>I ended up renaming the Field class to InnerField, and creating a facade/wrapper style structure around it like this:</p> <pre><code>Public Class Field Implements BusinessObjects.IField Private InnerField As BusinessObjects.IInnerField Public Sub New(ByVal field As IInnerField) InnerField = field End Sub ... Public ReadOnly Property IsDirty() As Boolean Implements BusinessObjects.IField.IsDirty Get Return InnerField.IsDirty End Get End Property ... End Class </code></pre> <p>This seems to be working out pretty well. Internally, the InnerField is suitably open and we have the freedom to make it more open in the future without impacting end-developers, and externally the Field class provides the simplified, locked down tool that end-developers need.</p> <p>So, assuming that was coherent, I was wondering how you might have proceeded in this situation, and whether my solution seems reasonable from the outside.</p> <p>Thanks!</p>

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