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POArc Error ?? Existing ivar delegate for unsafe_unretained property
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  1. POArc Error ?? Existing ivar delegate for unsafe_unretained property
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    copied!<p>I am currently following the tutorials in a book that was written before the use of arc in Xcode. I have the exact same problem like what is stated here: </p> <p><a href="https://stackoverflow.com/questions/8138902/existing-ivar-delegate-for-unsafe-unretained-property-delegate-must-be-un">&#39;Existing ivar &#39;delegate&#39; for unsafe_unretained property &#39;delegate&#39; must be __unsafe_unretained</a></p> <p>The question has been answered, but is has not been stated exactly why this is the case.</p> <p>The Code in the book states that I use this code to declare member variables:</p> <pre><code>the.h File ___________ #import &lt;Cocoa/Cocoa.h&gt; @interface TestProgramDelegate : NSObject &lt;NSApplicationDelegate&gt; { NSWindow *window; NSTextField *message; } @property (assign) IBOutlet NSWindow *window; @property (assign) IBOutlet NSTextField *message; @property (assign) IBOutlet NSTextField *inputText; @end the.m file __________ #import "the.h" //File @implementation theHFileAppDelegate @synthesize window @synthesize message @synthesize inputText </code></pre> <p>When I synthesize the variables in my .m file, I get the following error message: Existing ivar 'window' for property 'window' with assign attribute must be __unsafe_unretaied.</p> <p>But when I remove the declaration of the member variables like its stated in the book, everything works fine and I don't get an error.</p> <pre><code>the.h File ___________ #import &lt;Cocoa/Cocoa.h&gt; @interface TestProgramDelegate : NSObject &lt;NSApplicationDelegate&gt; { NSWindow *window; NSTextField *message; } @property (assign) IBOutlet NSWindow *window; @property (assign) IBOutlet NSTextField *message; @property (assign) IBOutlet NSTextField *inputText; @end the.m file __________ #import "the.h" //File @implementation theHFileAppDelegate @synthesize window @synthesize message @synthesize inputText </code></pre> <p>My program works, but I want to understand why this causes trouble. Thanks a lot.</p>
 

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