Re: error building Expressions: Can't resolve path component

From: Zvonimir Spajic (z.spaji..scensys.de)
Date: Mon May 02 2005 - 11:00:08 EDT

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    thank you Cris,
    thank you Andrus,

    it helps.

    Zvonimir

    On Mon, 2 May 2005 09:35:07 -0400, Cris Daniluk
    <cris.danilu..laraview.com> wrote:

    > Zvonimir,
    >
    > If you only have the category id and not the actual Category object, I
    > personally like to retrieve the object separately using DataObjectUtils
    > (pragmatically, you need to use the pk from time to time, but the less
    > time
    > you spend internally communicating with pks, the better). This lets you
    > use
    > the method Andrus recommended. It might be an extra step, but it pays
    > dividends in terms of clean code. On top of that, it may not even
    > trigger a
    > db lookup!
    >
    > An example:
    >
    > Category category = (Category) DataObjectUtils.objectForPk(context,
    > Category.class, categoryId);
    >
    > Hope that helps,
    >
    > Cris
    >
    >> Hi Zvonimir,
    >>
    >> The cleanest way is probably to use a Category object as a
    >> match parameter:
    >>
    >> Category catgeory = // ... obtain this object instead of usig id
    >> Expression e = ExpressionFactory.matchExp("hasCategory", category);
    >>
    >> However if you want to match on an id, you should use "DB" flavor of
    >> expressions. E.g.:
    >>
    >> Expression e =
    >> ExpressionFactory.matchDbExp("hasCategory.id", categoryId);
    >>
    >> BTW, if you use Expression.fromString, Cayenne is using "db:"
    >> prefix to
    >> distinguish between object and database path (e.g:
    >> "db:hasCategory.id").
    >>
    >> Hope this helps.
    >>
    >> Andrus
    >>
    >>
    >> > I tried something out, and is
    >> > this the best solution?
    >> >
    >> > Without defining the id in the path (hasCategory.id), only write
    >> > hasCategory:
    >> >
    >> > ...
    >> > Expression qual_2 = ExpressionFactory.matchExp("hasCategory",
    >> > categoryId); ...
    >> >
    >> > Greets
    >> > Zvonimir
    >> >
    >> >
    >> >
    >> > On Mon, 02 May 2005 15:06:38 +0200, Zvonimir Spajic
    >> > <z.spaji..scensys.de> wrote:
    >> >
    >> >> Hello,
    >> >>
    >> >> 1) why it's not allowed to build an expression like this
    >> >> --> see qual_2 (error message: "Can't resolve path component:
    >> >> [Category.id]")
    >> >>
    >> >> ...
    >> >> Expression qual_1 =
    >> Expression.fromString(SomeObject.NAME_PROPERTY + "
    >> >> likeIgnoreCase '%" + name + "%'");
    >> >> Expression qual_2 = ExpressionFactory.matchExp("hasCategory.id",
    >> >> categoryId);
    >> >> qual_1 = qual_1.andExp(qual_2);
    >> >> SelectQuery query = new SelectQuery(SomeObject.class, qual_1);
    >> >> ...
    >> >>
    >> >> -id is the PK-Column of category table
    >> >>
    >> >> 2) what is the best solution in this cases.
    >> >>
    >> >> Thanks for help
    >> >> Zvonimir Spajic
    >>
    >>
    >>
    >>
    >
    >
    > 

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