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copied!<h2>I think that "Doing work in the constructor" is okay...</h2> <p>... as long as you don't violate <a href="http://en.wikipedia.org/wiki/Single_responsibility_principle" rel="noreferrer" title="Single Responsibility Principle (SRP)">Single Responsibility Principle (SRP)</a> and stick to using <a href="http://en.wikipedia.org/wiki/Dependency_injection" rel="noreferrer" title="Dependency Injection (DI)">Dependency Injection (DI)</a>. </p> <p>I have been asking myself this question too lately. And the motivation against doing work in the constructor that I have found are either:</p> <ul> <li>It makes it hard to test <ul> <li>All examples I have seen have been where <a href="http://en.wikipedia.org/wiki/Dependency_injection" rel="noreferrer" title="Dependency Injection (DI)">DI</a> wasn't used. It wasn't actually the fault of the constructor doing actual work.</li> </ul></li> <li>You might not need all the results that your constructor calculates, wasting processing time and it's hard to test in isolation. <ul> <li>This is basically a violation of <a href="http://en.wikipedia.org/wiki/Single_responsibility_principle" rel="noreferrer" title="Single Responsibility Principle (SRP)">SRP</a>, not a fault of the constructor doing work per say.</li> </ul></li> <li>Old compilers have/had trouble with exceptions thrown in constructors, hence you shouldn't do anything other than assign fields in constructors. <ul> <li>I don't think it's a good idea to write new code taking historical compiler deficiencies into account. We might as well do away with C++11 and all that is good all together if we do.</li> </ul></li> </ul> <h2>My opinion is that...</h2> <p>... if your constructor needs to do work for it to adhere to <a href="http://en.wikipedia.org/wiki/Resource_Acquisition_Is_Initialization" rel="noreferrer" title="Resource Aquisition Is Initialization (RAII)">Resource Acquisition Is Initialization (RAII)</a> and the class does not violate <a href="http://en.wikipedia.org/wiki/Single_responsibility_principle" rel="noreferrer" title="Single Responsibility Principle (SRP)">SRP</a> and <a href="http://en.wikipedia.org/wiki/Dependency_injection" rel="noreferrer" title="Dependency Injection (DI)">DI</a> is properly used; Then doing work in the constructor is A-Okay! You can even throw an exception if you'd like to prevent usage of a class object whose initialization failed completely instead of relying on the user to check some return value.</p>

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