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    <p>It depends on how you want to use the variable. If you place the variable declaration inside the interface for your class, each instance of your class will have its <em>own</em> copy of the variable, which is kept separate from all other instances of your class:</p> <pre><code>@interface AppsController : NSObject { NSMutableArray *personArray; } </code></pre> <p>Each instance of the <code>AppsController</code> class will have its own copy of the <code>personArray</code> variable, which is separate from all other instances of the class.</p> <p>If, however, you define the variable <em>outside</em> of the interface, it becomes a global variable, and it is a <em>shared</em> (instances of your class do not get their own copy), and can be accessed from any instance of your class. If you declare it in the header as such:</p> <pre><code>NSMutableArray *personArray; </code></pre> <p>it is also visible to methods in other files and classes that include your header.</p> <p>If you declare the variable in the implementation file, but outside of the implementation itself, and prefix it with the <code>static</code> keyword, the variable will only be visible to the implementation of your class. This is common when you want a variable that is visible to you all of class instances, but not visible to anyone else, and is a way to create class variables.</p> <p>Since your object is a controller object, I am guessing that you only have one instance of it present in your application. You should declare the variable either:</p> <ol> <li>As an instance variable if your <code>personArray</code> variable needs to be <em>unique</em> to each instance of your controller class (even if you only have one instance now, you may have more than one instance of it in future).</li> <li>As a class variable (using the <code>static</code> keyword) if you want the variable to be visible to all instances of your class, with only one, shared instance of the variable.</li> <li>As a global variable if you want the variable to be a single instance (not unique to instances of your class) and also visible to other classes or code in other files.</li> </ol>
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Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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