Re: EOModel derived attributes

From: getsharp (getshar..mail.com)
Date: Mon Feb 09 2009 - 20:29:30 EST

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    Thanks Chuck.

    Prototype creation is uncharted territory for me.

    I'll go and have a read.

    Cheers,

    Sharpy.

    On 10/02/2009, at 11:04 AM, Chuck Hill wrote:

    >
    > On Feb 9, 2009, at 4:59 PM, getsharp wrote:
    >
    >> I only use derived attributes to represent a concatenation of
    >> several columns as a single attribute, eg fullName =
    >> CONCAT(first_name,' ',last_name)
    >>
    >> It's helpful for building qualifiers, eg fullName = 'Joe Citizen'
    >>
    >> Two things bug me though:
    >>
    >> * non standards compliant databases leaving me with database
    >> specific syntax in my model (I'm looking at you MySQL as per my
    >> example)
    >
    > That is because you are not using prototypes for this and you should
    > be. Database specific knowledge belongs in a prototype. Define a
    > "fullName" prototype for each database and use this to define the
    > attribute.
    >
    >
    >
    >> * displaying derived attributes where an EO is not a result of a
    >> database fetch, eg newly inserted EOs
    >
    > Override fullName to return firstName() + " " + lastName()
    >
    >
    >> It's probably less pain to just add methods to my Entity classes
    >> for a) returning concatenated attribute values and b) returning
    >> qualifiers in cases where I want to keep the clutter of building
    >> them out of components.
    >>
    >> The small win of having ease of qualification results in 2 things
    >> that bug me!
    >>
    >> Any thoughts on this?
    >
    >
    >
    > Looks solved to me. ;-)
    >
    > Chuck
    >
    >
    > --
    > Chuck Hill Senior Consultant / VP Development
    >
    > Practical WebObjects - for developers who want to increase their
    > overall knowledge of WebObjects or who are trying to solve specific
    > problems.
    > http://www.global-village.net/products/practical_webobjects
    >
    >
    >
    >
    >
    >



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