Hi All,

I'm coding a virtual rabbit pedigree app. (SL Ozimals system, doesn't really matter, the concept is simple)


Each bunny in my bunnies table can have a mother and a father, both members of that same bunnies table. Each bunny has a field "father_id" and "mother_id" which points back to a record of that same table.

Anny suggestions on how I'd code that? I see examples on the internet that code a system for one-parent, but nowhere for 2 parents.

I tried extending the Bunny model class to FatherBunny and MotherBunny, but got a bunch of errors, so I aborted that (guess general OOP practices don't apply to cake anymore cause it ain't pure MVC...)

If anyone can point me in the righti direction, that would be great.

thanks in advance,
Marv

Fortunately, part of what you want is described quite nicely in the docs! See http://book.cakephp.org/view/1046/Multiple...-the-same-model.

To associate a bunny with its parents, you'll probably want something like this in your Bunny model:

Hey apsillers,

thx for the swift reply!

I could've sworn that I'd already tried that, but I think I used a hasOne instead of a belongsTo relationship (linguistically "a bunny has one father" means the same as "a bunny belongs to a father", but I guess there's a difference in OOP terminology which i didn't quite comprehend, and to be honest still don't, but I'll study that further today )


Anyway I pasted in the 2 variables you provided but then came up with this error:

P.S.: Found this on a Rails forum (http://stackoverflow.com/questions/899981/...s-to-vs-has-one)

The way I always remember hasOne vs. belongsTo is this:

Think about what the hasMany relationship means in database terms, and then replace "many" with "one".

"A hasMany B" means there are many B records that point to any given A
"A hasOne B" means that there is one B record that points to any given A

On the other hand, "B belongsTo A" means that every B knows innately which A it belongs to, because it has a field pointing to some A. If you found that B lying by the side of the road, you'd know immediately which A it belonged to, because it has the A's id stamped right on it.

And as for your problem above: could identify and share exactly what bit of code is giving you that error?

Hey Apsillers,

First off thanks for your time looking into this. I know I'm a total MVC n00b, but I hope I can get the hang of it with the help of helpful ppl like yourself.

1) I have another issue with my index listing, but I'll probably be able to solve that when I get the relations straight. For some reason the controller method index() that creates the $bunnies variable in the index View with this line of code:
[PHP]
$this -> set('bunnies', $this -> Bunny -> find('all', Array('order' => 'Bunny.name ASC')) );
[/PHP]

messes up REALLY bad. When I print_r the $bunnies array only a fraction of the data from the tables is included in this multidim array even thought the data is present in the tables.

Again, this might be due to my crappy understanding of Cake's MVC implementation which seamlessly brings me to the next item


2) Let's see if I'm getting this straight:

Each bunnies record has an 'ear_type_id' field which points to the table "ear_types"

1) See my response to point #3 below, since its directly related to your #1.


2) Here is another hasMany/hasOne/belongsTo example, using people owning cars:

If I (a person) want to show that a car belongs to me, I can write my name on it. Every time I collect a new car, I write my name (or, really, my id) on it to show it belongs to me. If you find a car, you can see which person that car belongs to by checking what name/id is written on it. The car has a property (in CakePHP, it's called person_id) that points to its owner.

Thus, a person hasMany cars; the person_id written on each car points to its owner, and a person may have many cars pointing to them.

If we pass a law that says each person may have only one car, then we've just redefined the relationship so a person hasOne car. the owner of each car is still identifiable by looking at the name/id on the car (so car belongsTo person, still) but we're certain that each person has exactly one car.

And so:

You are correct that EarType hasMany Bunny; there are many Bunnies that point to any given EarType (just like many cars point to any given person). However, this means that Bunny belongsTo EarType. Each bunny records holds an id for an EarType -- this means it belongsTo earType, just like the cars held their owner's id.

- The act of pointing (i.e. knowing something else's id) implies belonging to the target. Think of the foriegnKey here as a pointer to a record's owner, like writing your name on stuff you own.

- Being pointed at implies having everyone who points at you. The foreignKey in a hasMany/hasOne relationship indicates how the other class will point at this object.

In both cases your foreignKey should be ear_type_id, since that's how bunny points to EarType and how EarType is pointed to by Bunny


3) The reson you're getting the error is that the find() operation is trying to get models related to the ones you requested, since find() by default helpfully returns objects directly related to the objects you asked to find. This is because of the "recursion=1" setting in find() (if you set recursion to 2, for example, it would do even more and return objects that were two relationships away).

Anyway, that just explains why "Children" has shown up at all. I am not sure what is actually going wrong when trying to fetch a Bunny's children. I'd suggest stripping down the finderQuery SQL to something really basic, then slowly building it back up, and see at what point it breaks. (Do this after you fix the other relationships, though.)

One more thing: all of your hasOne relationships should be belongsTo relationships, and the foreignKeys for all of them should be set to (whatever)_id, instead of just id.

(And you're quite welcome -- I'm just learning CakePHP myself, and I've found that the best way to learn it is to help other people with their own problems. It give me a reason me to read (and re-read) the docs a lot more, and think through tough CakePHP challenges. )

Good morning Apsillers (I don't know if it's morning where you live though, but still ),

1) It'll be easier to adress this once I've read the rest, indeed.

2) Please allow me to rephrase this in my own words and see if the concept made it to my brain OK:

a ) Marvelade hasMany books, but doesn't quite know by himself which ones. To keep track of this he does the following:
b ) In every book he writes on the first page "This book belongsTo Marvelade"

From looking at the first page of that book, Anyone can see who the owner is (provided that they know who I am ) , but if someone asked me "What books do you have" I couldn't accurately answer that, cause I don't keep a record of it; I just know that I have many, but that's just about it. Somehow every book returns to me after someone has borrowed it, because each of my books belongsTo me ('cause it says so on the first page).

Actually the bold parts in my quote from yesterday make much more sense to me now:

Ok, so I completely cut out the Children node from the hasMany var and the result is the same (except the error is gone ).

What I apparently needed to do was also eliminate the "conditions" key from the Mother and Father aliases so now I can reach the mother in the view using $bunny['Mother']['Name'], which only returned data for 3 of my 70+ bunnies when there was still a condition of Bunny.sex='Female' resp. Bunny.sex = 'Male'....

Those 3 bunnies were either fathers who had at least one son or mothers who had at least one daughter from the looks of it, so that kinda makes sense, since the condition was Bunny.sex and not Father.sex. Anyway, the program now acts as it's supposed to without those conditions. (at least the index view. I'm now struggling with the edit view which apparently is a whole other story )

For clarity, here's my revised bunny.php model class:

[PHP]<?php

class Bunny extends AppModel
{
var $name = "Bunny";

var $belongsTo = array(


'Mother' => array(
'className' => 'Bunny',
'foreignKey' => 'mother_id'
),

'Father' => array(
'className' => 'Bunny',
'foreignKey' => 'father_id'
),

"EyeColor" => array(
'className' => 'EyeColor',
'foreignKey' => 'eye_color_id'
),

"MainType" => array(
'className' => 'MainType',
'foreignKey' => 'main_type_id'
),


"SubType" => array(
'className' => 'SubType',
'foreignKey' => 'sub_type_id'
),


"EarType" => array(
'className' => 'EarType',
'foreignKey' => 'ear_type_id'
),


"Shade" => array(
'className' => 'Shade',
'foreignKey' => 'shade_id'
),



);

}

?>
[/PHP]

Excellent! Glad you're getting somewhere.

And, yes, from your example, you understand hasMany/hasOne/beongsTo perfectly. As you said, if a person hasMany books, there's no way for a Person record to have hold all of its related Book keys. The books hold their person_id, because they belongTo a person. So just remember that 1) hasMany doesn't know any of its related keys and that 2) hasOne works the same way as hasMany, in terms of keys.

Well, it looks like you've gotten past the original issues in this post, so I guess you can start new threads for any new issues you run into.

See you around!

I have a basic version running now, but I have some features I want to add. I'll post new topics as I run into problems (which will most likely happen ).

Thanks for your immense help so far; it's really appreciated.



Best regards,
Marv