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This article introduces the knowledge of "how C++ uses std::weak_ptr to break the cycle caused by share_ptrs". In the operation of practical cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

R.24: use std::weak_ptr to break the cycle caused by share_ptrs

Reason (reason)

Shared_ptr relies on counting actions, and loop constructs (such as holding shared_ptr each other) can cause counts to never return to zero, so we need a mechanism to break this cycle.

Example (sample)

# include

Class bar

Class foo

{

Public:

Explicit foo (const std::shared_ptr& forward_reference)

: forward_reference_ (forward_reference)

{}

Private:

Std::shared_ptr forward_reference_

}

Class bar

{

Public:

Explicit bar (const std::weak_ptr& back_reference)

: back_reference_ (back_reference)

{}

Void do_something ()

{

If (auto shared_back_reference = back_reference_.lock ()) {

/ / Use * shared_back_reference

}

}

Private:

Std::weak_ptr back_reference_

}

Enforcement (implementation recommendations)

It's almost impossible. If you can statically check for loops, we won't need weak_ptr.

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