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    <p>What you're asking is not really possible.</p> <p>The <strong>only</strong> way to prevent something from being assigned is to define the <code>operator =</code> for that type as <code>private</code>. (As an extension of this, since const <code>operator =</code> methods don't make much sense (and are thus uncommon) you can come close to this by only allowing access to const references from your container. But the user can still define a const <code>operator =</code>, and you want mutable objects anyways.)</p> <p>If you think about it, <code>std::vector::operator []</code> returns a reference to the value it contains. Using the assignment operator will call <code>operator =</code> for the value. <code>std::vector</code> is completely bypassed here (except for the <code>operator[]</code> call used to get the reference in the first place) so there is no possibility for it (<code>std::vector</code>) to in any way to override the call to the <code>operator =</code> function. </p> <p>Anything you do to directly access the members of an object in the container is going to have to return a reference to the object, which can then be used to call the object's <code>operator =</code>. So, there is no way a container can prevent objects inside of it from being assigned unless the container implements a proxy for the objects it contains which has a private assignment operator that does nothing and forwards other calls to the "real" object, but does not allow direct access to the real object (though if it made sense to do so, you could return copies of the real object). </p>
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    1. POnon-resizeable vector/array of non-reassignable but mutable members?
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    1. POnon-resizeable vector/array of non-reassignable but mutable members?
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    1. COThat's not entirely correct. The `std::vector` itself may be declared `const`. Once that is done, the `const` form of `std::vector::operator[]` is called, which returns a `const` reference to the object. Once that is done, only `const` methods in the object may be called through that `const` reference. Those `const` methods can only modify data members that are declared `mutable`. AFAICT, this behavior is what @Jeff is looking for. See my answer for an example.
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    2. COI believe what he wants is a way to return non-const objects from the const vector (so that he doesn't have to have const members and mutable data in order to work with them). Also, as I mentioned, you can make a const operator = which will assign the mutable data members, so you can still assign to a const object in that case.
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    3. COWhat's wrong with having `const` methods and `mutable` data? The question focuses on how to achieve the desired behavior. `const` methods and `mutable` data is certainly one way to do so without resorting to proxies, `friend` s, etc.
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