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    <p>If you are using a dependency-injection framework, then the common way to handle this is to either pass in a PermissionsManager object in the constructor or to have a property of type PermissionsManager that the framework sets for you. </p> <p>If this is not feasible, then having users get an instance of this class via factory is a good choice. In this case, the factory passes the PermissionManager in to the constructor when it creates the class. In your application start-up, you would create the single PermissionManager first, then create your factory, passing in the PermissionManager.</p> <p>You are correct that it is normally unwieldy for the clients of a class to know where to find the correct PermissionManager instance and pass it in (or even to care about the fact that your class uses a PermissionManager).</p> <p>One compromise solution I've seen is to give your class a property of type PermissionManager. If the property has been set (say, in a unit test), you use that instance, otherwise you use the singleton. Something like:</p> <pre><code>PermissionManager mManager = null; public PermissionManager Permissions { if (mManager == null) { return mManager; } return PermissionManager.getInstance(); } </code></pre> <p>Of course, strictly speaking, your PermissionManager should implement some kind of IPermissionManager interface, and <strong>that's</strong> what your other class should reference so a dummy implementation can be substituted more easily during testing.</p>
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    1. USEddie Deyo
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    1. COThe point about injecting via an interface is an important one. The ability to mock the PermissionManager object in tests is what makes DI a powerful approach for more testable code.
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      1. USMike Furtak
    2. COwhat if PermissionManager itself has a dependency. Is there a less weird way than PermissionManager.getInstance(Foo)? ?
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      1. USLouis Rhys
 

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