Question

Trying to store currency, that can be in the negative/postive, with decimals. I’ve done much searching and found that using Decimal type in the model is the best way. That doesn’t seem to be signed thought. I see you can store a signed integer (no decimals). But I can’t find any info on storing a signed, decimal number.

Since I’m not finding anything, I’m guessing you can’t.
If so, how do you go about storing this kind of info? Create a boolean attribute that describes if the amount is neg/pos?

Answer 1

The “Decimal” type in CoreData uses the SQLite “Decimal” storage class, which is backed by the “Real” storage class.

This will support negative numbers at the store level:

sqlite> .tables
test
sqlite> .schema
CREATE TABLE test (pk integer primary_key, d double, f float, r real);
sqlite> insert into test (d,f,r) values (-1.0, -1.5, -1.252853);
sqlite> select * from test;
|-1.0|-1.5|-1.252853

As you can see, SQLite correctly stores the value.

In your objective C code you will be working with the NSNumber class, which can be instantiated with negative decimals using the following code:

[NSDecimalNumber numberWithDouble:-1.57];
[NSDecimalNumber numberWithFloat:-1.57];