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Anonymous users2024-02-05copy : Create an object with an index count of 1 and then release the old object.
retain: Releases the old object, assigns the value of the old object to the input object, and raises the index count of the input object to 1
So what the hell does it mean?
copy actually creates an identical object, while retain is not
For example, an nsstring object with an address of 0 1111 and a content of @"str".
After copying to another nsstring, the address is 0 2222, the content is the same, the new object retains 1, and the old object remains unchanged.
After retaining to another nsstring, the address is the same (create a pointer, pointer copy), the content is of course the same, and the object has a retain value of +1
That is, retain is a copy of the pointer, and copy is a copy of the content.
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Anonymous users2024-02-04retain, which is a shallow copy, does not change the object it points to, and the reference counter is added by 1 for MRC.
copy, which is a deep copy, re-copies an object, the original object does not change, and the newly copied object, the reference counter is added by 1
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Anonymous users2024-02-03Reply,It's wrong.,Copy and mutablecopy are deep copies.,And copy can also be modified.,You can try to copy a string in the modification.,The result can be changed.,It doesn't affect the original string.,The original string is still there after the original string is released.,So the landlord is really a mistake!!
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Anonymous users2024-02-02Assign is used for simple data types, such as nsinteger, double, bool, retain and copy for objects, copy is used when A points to an object, B also wants to point to the same object, if you use assign, if A releases, and then call B will crash, if you use copy, A and B each have their own memory, you can solve this problem.
retain will add one to the counter, which can also solve the problem of assign.
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With the addition of atomic, the setter function will look like this: if (property !).= newvalue)
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