[pclasses-devel] properties class

[stephan b. <st...@s1...>]

Yo!

Marc sent me some code today for P1 with his latest, feature-filled 
Property classes. Those aren't yet ported to p2. In the mean time, i 
took and old property store class of mine and use LexT to simplify the 
interface (cut the interface in half!). See 
P::Util::SimplePropertyStore. It's simply a key/val pair holder, and 
doesn't support multiple keys at the moment - we should decide if it 
should use multimap or map. i vote for map, because that's what all of 
my anticipated use-cases will need, and multimap doesn't support 
operator[].

Here's a short demo, including SIO support:

	using namespace ::P::SIO;
	using namespace ::P::Util;
	P::Util::SimplePropertyStoreTest m;
	m["fred"] = "wilma";
	m["barney"] = "betty";
	m["days_in_december"] = 31;
	m["days_in_february"] = 28.5;
	m["the_letter_a"] = 'a';
	save( m, std::cout );

Output:

<!DOCTYPE s11n::io::expat_serializer>
<s11n_node class="SomeSillyPropertyMap">
        <barney>betty</barney>
        <days_in_december>31</days_in_december>
        <days_in_february>28.500000</days_in_february>
        <fred>wilma</fred>
        <the_letter_a>a</the_letter_a>
</s11n_node>

Couldn't get much simpler than that. :)

The i/o support works with so little effort because:

a) LexT is i/ostreamable, which means we can inherently treat it as a 
POD.

b) SimplePropertyStore is close to API-compatible with std::map, which 
means we can plug it in to P::SIO using the already-available map 
serialization proxies:

#define PS11N_TYPE P::Util::SimplePropertyStore
#define PS11N_TYPE_NAME "SomeSillyPropertyMap"
#define PS11N_SERIALIZE_FUNCTOR \
   ::P::s11n::map::streamable_map_serializable_proxy
#include <pclasses/s11n/reg_serializable_traits.h>


What does that mean? It means streamable_..._proxy will act on behalf of 
our type for serialization calls. If we swap that proxy out with the 
default map proxy:
	::P::s11n::map::map_serializable_proxy
then we get MUCH fatter output. The advantage to the default proxy is 
that it works with all objects, not just i/ostreamables. The output 
when we treat each map entry as a POD:

<!DOCTYPE s11n::io::expat_serializer>
<s11n_node class="SomeSillyPropertyMap">
        <pair class="pair">
                <first class="string">
                        <v>barney</v>
                </first>
                <second class="LexT">
                        <v>betty</v>
                </second>
        </pair>

... repeat for each pair ...

</s11n_node>


When we KNOW we're saving POD-style data we can plug in lighter-weight, 
more specialized proxies.

See ya!


-- 
----- st...@s1...   http://s11n.net
"...pleasure is a grace and is not obedient to the commands
of the will." -- Alan W. Watts