What is IOS retain do at backend [closed]

问题

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Closed 7 years ago.

Consider I am allocating an object. Please see the below image

In the above image *myObject is a pointer. It is referring to an space allocated to that object. When we retain the object, I like to know what it does at backend. Also I like to know why we are doing that.

Also when we release it how it works at backend.

I also like to know what happens at backend when we copy an object.

I am really sorry if my question is so basic.

回答1:

What retain actually does under the hood is:

1. Take a global lock in the objc runtime
2. Look up a hash table entry based on the pointer to the object being retained
3. Increment a counter in that entry
4. Release the lock

I don't expect this to be all that helpful in practice, but I think it's what you were asking for.

来源：https://stackoverflow.com/questions/12990128/what-is-ios-retain-do-at-backend