Re: predicate for a Core Data fetch request rejected by SQL
Re: predicate for a Core Data fetch request rejected by SQL
- Subject: Re: predicate for a Core Data fetch request rejected by SQL
- From: Joanna Carter <email@hidden>
- Date: Fri, 5 Mar 2010 23:45:50 +0000
Hi Sean
> But you shouldn't have to... Core Data is "not a database" and its use
> of SQL is an implementation detail. One shouldn't have to know anything
> about SQL to use Core Data. Of course, in practice, such knowledge is
> helpful, as you say.
You have a point but, in theory, predicates against lists of objects usually take either the form:
<value of a property> <operator> <constant value>
... or possibly:
<value of a property> <operator> <value of another property>
Some predicates might be usable between two constant values but I have never seen one used, even with lists of objects, as:
<constant value> <operator> <value of a property>
Such a construct might work in the context of an XML file because the lefthand term could be interpreted as the name of a key but, not normally in a where clause in a database.
Joanna
--
Joanna Carter
Carter Consulting
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