title: Why one may need a shared_from_this instead of directly using this pointer?
body: <p>Look at the second answer here:
  <a href="https://stackoverflow.com/questions/36041012/what-is-the-need-for-enable-shared-from-this">What is the need for enable_shared_from_this?</a></p>
  
  <p>it says:
  "Short answer: you need enable_shared_from_this when you need to use inside the object itself existing shared pointer guarding this object.</p>
  
  <p>Out of the object you can simply assign and copy a shared_ptr because you deal with the shared_ptr variable as is."</p>
  
  <p>and later down in the last line it says:
  "And when and why one can need a shared pointer to this instead of just this it is quite other question. For example, it is widely used in asynchronous programming for callbacks binding."</p>
  
  <p>Here in this post I want to ask exactly this other question. What is an use case for "enable_shared_from_this" and "shared_from_this"?</p>