Hi Henk,
this is fairly easy to implement yourself using an intermediate join
table and by writing the database logic yourself. Sadly I don't
really have the time to detail this step by step, but I'll probably
write something about it in on of the upcoming books.
In the meantime, I'm looking into adding native support for this to
RIFE and RIFE/Crud.
This is what I'm thinking about at the moment. Anyone, please feel
free to give comments and ideas about how to do this best.
* add a new manyToMany(Class klass) constrain to ConstrainedProperty
The property type related to the named property should be a
collection or an array of integers. It will not be mapped to a column
in the table of the bean class. Instead, it will work with an
intermediate join table. The name of the table is
tablename1_tablename2, the names are those of the tables that are
present in the many to many relationship and they are alphabetically
ordered (so that reverse a manyToMany constraint on the second class
would use the same link table). The link table will have two columns
that have the same names as the identifier columns of linked tables,
prefixed with their table name.
For example, considering your Band and Musician classes, you'd have a
band_musician join table with the columns band_id and musician_id.
* the manyToMany constrained property will be auto-populated during
select and contain the identifier values of the associated ids.
* during save, insert and update, these ids will be stored
automatically in the join table and any previous values for the
entity in the join table will be removed first.
* Delete will simply remove the correct values from the join table
* the install and remove methods will also create and remove the join
table
Now, related to RIFE/Crud.
* when the manyToMany constraint is present, a multi select list will
be shown for the property that uses the textual identifier (just as
with manyToOne)
* when only an association constraint is present towards a manyToMany
class, the textual identifier values of associated class are simply
listed, and a link is present to go to each individual entity directly
What do you think of this?
Best regards,
Geert
On 19 May 2006, at 00:28, henk wrote:
Ok. I have two tables : Band and Musician. A Band contains
different Musicians and a Musician can play in different Bands. So
I need an interface for editing a Band in which I can choose from
the list of available Musicians (e.g. a html SELECT MULTIPLE), the
ones that play in this Band. It would also be nice to see in the
Musician overview, in which Bands he/she plays.
Fairly simple, and I can code this from scratch. But if I can
integrate this with my other Crud editors, it would be even nicer.
thanks
Henk
Geert Bevin wrote:
Hi Henk,
can you give a brief description of what your many-to-many
interface should have to do?
Best regards,
Geert
On 18 May 2006, at 12:58, Henk wrote:
Hi,
I am using Rife/crud in my application and it works very nice. I
even figured out how to link directly to the add and browse
things so I can use my own administration interface. So far so
good. The sad thing is I also need an interface which allows
many-to-many relationships. I searched troughout the site and
mail archives, and I understand this is not possible out-of-the-
box. No problem, I don't mind to code. But I badly need an
example or good advice on how to proceed. I think have to use my
own element implementation. Can you point me to some example ?
Sorry to ask this once again, if I find a decent way to do this,
I can maybe post it somewhere.
Keep up the good work !
Henk
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