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Polymorphic copy: Difference between revisions
→{{header|Objective-C}}
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All objects inherit the <code>copy</code> method from <code>NSObject</code>, which performs copying. But they must implement the <code>copyWithZone:</code> method to actually specify how to copy. Calling <code>copy</code> on an object that does not implement <code>copyWithZone:</code> will result in an error.
Implementing copying can be done with the <code>NSCopyObject()</code> function for a simple byte-for-byte shallow copy of the object fields. Or you can do something more complicated like explicitly allocate a new object of a certain class (but then it won't really be polymorphic) and initialize it with your object's data. I am not really clear on the details of this.
<lang objc>
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// or:
// T *copy = [[T allocWithZone:zone] init]; // call an appropriate constructor here
// // then copy data into it as appropriate here
// return copy;
}
@end
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</lang>
=={{header|OCaml}}==
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