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POObjective-c: why private ivars are not hidden from the outside access when using KVC
 

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  1. POObjective-c: why private ivars are not hidden from the outside access when using KVC
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    <p>After trying to access ivars using KVC, I have noticed that there was no protection on private and protected ivars. It doesn't matter what I put a in front of the ivar (private or protected keyword) - an ivar is always a public ivar when using KVC method "setValue". Here is my code where all of the seven ivars and properties are changeble outside the class instance:</p> <pre><code>//************ interface file ***************// @interface MyClass : NSObject { @public NSNumber *public_num; @protected NSNumber *protected_num; @private NSNumber *private_num; NSNumber *private_property; } @property (retain) NSNumber *public_property; @property (retain) NSNumber *private_property; @end //********* implementation file *********// @interface MyClass(){ @private NSNumber *very_private_num; } @property (retain) NSNumber *very_private_property; @end @implementation MyClass @synthesize public_property, private_property, very_private_property; @end //****** main **********// MyClass *myClass = [[MyClass alloc] init]; [myClass setValue:[NSNumber numberWithInt:1] forKey:@"public_num"]; [myClass setValue:[NSNumber numberWithInt:2] forKey:@"protected_num"]; [myClass setValue:[NSNumber numberWithInt:3] forKey:@"private_num"]; [myClass setValue:[NSNumber numberWithInt:4] forKey:@"public_property"]; [myClass setValue:[NSNumber numberWithInt:5] forKey:@"private_property"]; [myClass setValue:[NSNumber numberWithInt:6] forKey:@"very_private_num"]; [myClass setValue:[NSNumber numberWithInt:7] forKey:@"very_private_property"]; NSNumber *l_public_num = [myClass valueForKey:@"public_num"]; NSNumber *l_protected_num = [myClass valueForKey:@"protected_num"]; NSNumber *l_private_num = [myClass valueForKey:@"private_num"]; NSNumber *l_public_property = [myClass valueForKey:@"public_property"]; NSNumber *l_private_property = [myClass valueForKey:@"private_property"]; NSNumber *l_very_private_num = [myClass valueForKey:@"very_private_num"]; NSNumber *l_very_private_property = [myClass valueForKey:@"very_private_property"]; NSLog(@"public_num = %@, protected_num = %@, private_num = %@, public_property = %@, private_property = %@, very_private_num = %@, very_private_property = %@", l_public_num, l_protected_num, l_private_num, l_public_property, l_private_property, l_very_private_num, l_very_private_property); </code></pre> <p>The result of the output> public_num = 1, protected_num = 2, private_num = 3, public_property = 4, private_property = 5, very_private_num = 6, very_private_property = 7. </p> <p>Even if the ivar declared at private interface, it is still changeable outside the class. So how do I have to enforce encapsulation and "to protect my ivars from evil other programmers" :) </p>
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    1. COSo far, I have noticed that the only way to have "sort of a private method" is to declare a pure method in private interface (without using synthesize). Then compiler warns about method being not found. But still code and the method is executable :). I wrote NSLog(@"Inside hiddenMethod\n") in the hiddenMethod and then executed that method from the main and I got the message in debug window. }
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    2. COThere are no private methods in Objective-C.
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