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    <p>Okay, there's nothing specifically wrong under the LoD about passing an implementation object, a "plugin" in the constructor. What's important is that the interface of the class doesn't tell you much <em>about</em> that implementation.</p> <p>If your interface to WebGetTask depends on the exact implementation of HttpService, <em>that</em> violates the Law of Demeter.</p> <p>The trick here is to think about the interface signature of WebGetTask. The name itself suggests that you're not quite following the Law of Demeter — or principle of least knowledge — because you're defining a class that (1) is defined as being specific for the web, and (2) is a verb instead of a noun.</p> <p>Now, neither of those is necessarily wrong, but they are both "OO smells" if you will, signs that you may not be thinking object-ly enough.</p> <p>So let's try "refactoring" the design. First thing, think about a GetTask that has no "web" associated with it. You can then, either at construction time or at some later time build a service object and pass it in. If it's HttpService, that's fine, but the user of your class doesn't need any information about what's under the covers. </p> <p>Second thing, let's make it a noun. Call it TaskFactory — your intuition was leading you right there — with a ctor that takes an IOService, which I've just invented as being the abstract interface implemented by HttpService.</p> <p>Now, you have (this is sort of Java/C++ pseudocode, don't get excited about syntax details): </p> <pre><code> class Task { ... } class TaskFactory { public TaskFactory(IOServer svc){...} public Task get(){...} } </code></pre> <p>and you use it by writing</p> <pre><code> TaskFactory fac = new TaskFactory(new HttpService()); Task tsk = fac.get(); </code></pre> <p>Now, we kow the minimum about the innards of TaskFactory, the IO service, and for that matter Tasks.</p>
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