My Core Data managed objects (instances) all have their own index.
Naturally, when I add an object, I want to set its index to the
highest index value so far, + 1. This should be done in -
awakeFromInsert.
However, when I perform a fetch request from there, a second (new)
item appears in the table (instead of just one). This can't be right.
So, the question is how to keep track of the maximum index in a
correct way.
Should I maintain a class variable for the maximum index (updated
on awakeFromFetch / -Insert)? If so, how do I keep track of removed
objects (say when the object with the highest index gets removed)?
Suggestions appreciated.
Arthur,
I would add to the data model an entity (say Info) to maintain the
maximum index. If I didn't need my object indices to be contiguous
then I would simply increment the index on insertion and do nothing
on deletion (rather than updating the indices of the remaining
objects and decrementing the maximum index). If I didn't mind having
gaps in the indices but wanted to reuse them when possible then I
would add a set of unused indices as a to-many relation of the Info
entity. These properties could be transient, but I think its much
simpler to make them persistent.
Cheers,
dave
Best regards,
Arthur C.
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