std::polymorphic<T, Allocator>::operator= - cppreference.com (original) (raw)

Replaces contents of *this with the contents of other.

Let traits be std::allocator_traits<Allocator>:

1. If std::addressof(other) == this is true, does nothing. Otherwise, let need_update be traits::propagate_on_container_copy_assignment::value:

1. If other is valueless, proceeds to the next step. Otherwise, constructs a new owned object in *this using traits::construct with *other as the argument, using the allocator update_alloc ? other._[alloc](../polymorphic.html#alloc "cpp/memory/polymorphic")_ : _[alloc](../polymorphic.html#alloc "cpp/memory/polymorphic")_.
2. The previously owned object in *this (if any) is destroyed using traits::destroy and then the storage is deallocated.

After updating the object owned by *this, if need_update is true, _[alloc](../polymorphic.html#alloc "cpp/memory/polymorphic")_ is replaced with a copy of other._[alloc](../polymorphic.html#alloc "cpp/memory/polymorphic")_.

1. If std::addressof(other) == this is true, does nothing. Otherwise, let need_update be traits::propagate_on_container_move_assignment::value:

• If _[alloc](../polymorphic.html#alloc "cpp/memory/polymorphic")_ == other._[alloc](../polymorphic.html#alloc "cpp/memory/polymorphic")_ is true, swaps the owned objects in *this and other; the owned object in other (if any) is then destroyed using traits::destroy and then the storage is deallocated.
• Otherwise:

1. If other is valueless, proceeds to the next step. Otherwise, constructs a new owned object in *this using traits::construct with std::move(*other) as the argument, using the allocator update_alloc ? other._[alloc](../polymorphic.html#alloc "cpp/memory/polymorphic")_ : _[alloc](../polymorphic.html#alloc "cpp/memory/polymorphic")_.
2. The previously owned object in *this (if any) is destroyed using traits::destroy and then the storage is deallocated.

After updating the objects owned by *this and other, if need_update is true, _[alloc](../polymorphic.html#alloc "cpp/memory/polymorphic")_ is replaced with a copy of other._[alloc](../polymorphic.html#alloc "cpp/memory/polymorphic")_.

If all following conditions are satisfied, the program is ill-formed:

• std::allocator_traits<Allocator>::is_always_equal::value is false.
• T is an incomplete type.

[edit] Parameters

[edit] Return value

*this

[edit] Exceptions

1. If any exception is thrown, there are no effects on *this.

2. If any exception is thrown, there are no effects on *this or other.

[edit] Example