[Dbix-class] many_to_many data access

[Frank Schwach]

On 12/07/12 09:29, Patrick Meidl wrote:
> On Thu, Jul 12 2012, Robyn Jonahs<learn.catalyst at gmail.com>  wrote:
>
>> The cities, states and country relationships are all many_to_many so
>> once I have one, I can do the others.
> as I mentioned before, in terms of a clean database design, shouln't
> your relationships look like this: City belongs_to a State, which in
> turn belongs_to a Country. having city, state and country as independent
> many_to_many on the store violates the true relationships between these
> entities.

except if you are expecting international customers: in many countries 
there are no "states", so a city really only "might_have" a state and 
the city itself "belongs_to" a country, The (optional) state also 
"belongs_to" a country adn there is no need to establish the link 
between cities and states at all, not to mention the problem you might 
have in some countries where cities can even belong to more than one 
province.

Frank


> if you implement it like this, you would end up with code like this:
>
> foreach my $city ($store->cities) {
>    print "City: " . $city->city . "\n";
>    print "State: "  . $city->state->name . "\n";
>    print "Country: "  . $city->state->country->name . "\n";
> }
>
> you could also use the proxy attribute on your belongs_to relations to
> shortcut these calls to something like $city->state_name and
> $city->country_name.
>
> HTH
>
>      patrick
>


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