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This article mainly explains "how to use delete in C++ to prohibit default behavior", the content of the article is simple and clear, easy to learn and understand, now please follow the editor's train of thought slowly in depth, together to study and learn "how to use delete in C++ to prohibit default behavior" bar!

If default (and no other options) behaviors are not required, use = delete to disable them

Reason (reason)

In some cases, you may not want to have a default behavior.

Example (sample) class Immortal {

Public:

~ Immortal () = delete; / / do not allow destruction

/ /...

}

Void use ()

{

Immortal ugh; / / error: ugh cannot be destroyed

Immortal* p = new Immortal {}

Delete p; / / error: cannot destroy * p

} Example (sample)

Exclusive pointers can be moved, but cannot be copied. To achieve this, the code forbids copy operations. The way to prohibit copying is to declare the copy operation originating from the left value as = delete.

Template class unique_ptr {

Public:

/ /...

Constexpr unique_ptr () noexcept

Explicit unique_ptr (pointer p) noexcept

/ /...

Unique_ptr (unique_ptr&& u) noexcept; / / move constructor

/ /...

Unique_ptr (const unique_ptr&) = delete; / / disable copy from lvalue

/ /...

}

Unique_ptr make (); / / make "something" and return it by moving

Void f ()

{

Unique_ptr pi {}

Auto pi2 {pi}; / / error: no move constructor from lvalue

Auto pi3 {make ()}; / / OK, move: the result of make () is an rvalue

}

Note: forbidden functions should be public

By convention, the deleted function (deleted functions) is declared public, not private. When user code attempts to call a member function, C++ checks its accessibility (accessibility, is it public?) before checking its delete status bit. . When a user tries to call a delete function declared as private, some compilers complain that the deleted function is declared as private

Enforcement (implementation recommendations)

Eliminating the default action should be based on the expected semantics of the class. Doubt these classes, but at the same time maintain a "positive list" of classes whose content is determined to be the right thing.

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