[boost] class properties: request for promotion and/or fast review.

From: Gennadiy Rozental (gennadiy.rozental_at_[hidden])
Date: 2004-05-23 05:26:01

Hi,

I am using simple class properties facility for some time and found it quite
useful. Actually it's nothing fancy - simple helper classes to eliminate
repetitive setter/accessor methods (and no need for language extensions).

Essentially if you need simple readwrite property with trivial access
methods in you class you would instead of writing:

T member;

void set_member( T const& ) {...}
T const& get_member() {...}

would write:

readwrite_property<T> member;

Now any time you need to get a member value you would write

T t = obj.member;

while if you need to update the value:

obj.member.value = t;

It's not more nor less safe as usual get/set scheme.

If you need readonly object property that get initialized in constructor and
never updated you could use
readonly_property template for example like this:

class node {
public:
    readonly<std::string> p_name;
    ....

};

Now everywhere (almost) you could just use n.p_name. To get an access to
name member functions you could use operator-> like this:

n.p_name->size();

And nobody would be able to update readonly property value.

Finally if you need to provide a write access for readonly property you
could use another form of readonly_property template. Unfortunately during
language limitations (inability to declare template parameter as friend) you
would need to use macro, for example like this:

class foo {
public:
     BOOST_READONLY_PROPERTY( int, (foo)(Friend2) ) p_value;
     ...
};

Now only class foo and Friend2 have a write access to the value of the
property p_value;

If boosters find this functionality worth reusing I am ready to prepare
document page describing it's usage.
If we don't find this header eligible for review I would like to ask then
for permission to at least put these templates in boost namespace (currently
boost::unit_test), for it inconvenience for me to keep it in deep namespace
for rest of my current development.

Header you could see here:

http://tinyurl.com/38mcm

Regards,

Gennadiy.