Assume I have a thread-safe collection of Things (call it a ThingList), and I want to add the following function.

Thing * ThingList::findByName(string name)
{
  return &item[name]; // or something similar..
}

But by doing this, I've delegated the responsibility for thread safety to the calling code, which would have to do something like this:

try 
{
  list.lock(); // NEEDED FOR THREAD SAFETY
  Thing *foo = list.findByName("wibble");
  foo->Bar = 123;
  list.unlock();  
}
catch (...) 
{
  list.unlock();
  throw;
} 

Obviously a RAII lock/unlock object would simplify/remove the try/catch/unlocks, but it's still easy for the caller to forget.

There are a few alternatives I've looked at:

• Return Thing by value, instead of a pointer - fine unless you need to modify the Thing
• Add function ThingList::setItemBar(string name, int value) - fine, but these tend to proliferate
• Return a pointerlike object which locks the list on creation and unlocks it again on destruction. Not sure if this is good/bad practice...

What's the right approach to dealing with this?