Dirk Gregorius wrote:

I have four easy questions regarding boost::shared_ptr:

1.) How do I pass a boost::shared_ptr to a function - via value or reference?

void ByValue( boost::shared_ptr<Foo> pFoo ); void ByReference( boost::shared_ptr<Foo>& rFooPtr );

By value when the function wants to modify its own temporary copy of the argument; by const reference or by value (slightly less efficient, but often unnoticeable) when it's an immutable input argument; by non-const reference when it's an output argument. Same as with any other "medium-weight" type.

2.) When passing a raw pointee to a function you can declare the pointee const. How do I pass a const boost::shared_ptr?

void ConstRaw( const Foo* pFoo ); void ConstSharedPtr( ??? );

shared_ptr<Foo const> pFoo

3.) Does anything speak against passing a reference to a factory function instead of returning the boost::shared_ptr?

boost::shared_ptr<Foo> Create( void ) { return boost::shared_ptr<Foo>( new Foo ); }

bool Create( boost::shared_ptr<Foo>& foo ) { // Make some validations and return false on error. // ...

// Everyting is ok. Reset the pointee and return a success foo.reset( new Foo );

return true; }

No, but you can indicate failure by returning an empty shared_ptr from the first Create. if( shared_ptr<Foo> p = Create() ) { // do something } else { // Create failed }

4.) Can I test a boost::shared_ptr against NULL like a raw pointee?

Yes, the conversion operator that enables if( p ) tests also enables p == 0 comparisons as a side effect.