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    <p>Under the hood, Objective-C objects are basically C structs. Each one contains a field called <code>isa</code>, which is a pointer to the class that the object is an instance of (that's how the object and Objective-C runtime knows what kind of object it is).</p> <p>Regarding the initialization of variables: in Objective-C, instance variables are automatically initialized to <code>0</code> (for C types like <code>int</code>) or <code>nil</code> (for Objective-C objects). Apple's guidelines say that initializing your ivars to those values in your <code>init</code> methods is redundant, so don't do it. For example, say you had a class like this:</p> <pre><code>@interface MyClass : NSObject { int myInt; double myDouble; MyOtherClass *myObj; } @end </code></pre> <p>Writing your <code>init</code> method this way would be redundant, since those ivars will be initialized to <code>0</code> or <code>nil</code> anyway:</p> <pre><code>@implementation MyClass - (id)init { if ((self = [super init])) { myInt = 0; myDouble = 0.0; myObj = nil; } return self; } @end </code></pre> <p>You can do this instead:</p> <pre><code>@implementation MyClass - (id)init { return [super init]; } @end </code></pre> <p>Of course, if you want the ivars to be initialized to values other than <code>0</code> or <code>nil</code>, you should still initialize them:</p> <pre><code>@implementation MyClass - (id)init { if ((self = [super init])) { myInit = 10; myDouble = 100.0; myObj = [[MyOtherClass alloc] init]; } return self; } @end </code></pre>
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    1. POWhat does isa mean in objective-c?
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    1. USmipadi
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    1. COThanks for the answer i would like to know about this line. Don't initialize variables to 0 or nil in the init method; it's redundant. Where should we use this pattern. Does it mean that we should not initialize variable's in data Modal's
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      1. USRahul Vyas
    2. COFeel free to initialize your data -- just don't initialize your variables to `0` or `nil`.
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      1. USsarnold
    3. COsarnold basically explained it, but I updated my answer to address this issue.
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