CoreData：大量实体还是将数组存储为可变形？

Question

I am making a game where every creature can have 3 attacks and every attack can have many effects at the same time. I'm using CoreData to hold all of the data.

A basic example of what my problem is can be seen with three entities:

1. Creature : contains a to-many relationship to Attack entity
2. Attack : contains a to-many relationship to Effect entity
3. Effect : contains the details of the effect (damage, confuse, poison, etc)

So to begin I need to have three unique Attack entities for each unique Creature entity. Then I would need to add the Effect entities to each attack. My problem is that each effect can have a different value but it is basically the same effect as all the other creatures: It is still "Damage" but the value of the damage is different from each creature.

There are only two ways i've thought of doing this:

1. Create a unique Effect for each Attack for each Creature , this way I could store the effect value inside the entity. The disadvantage of this would be that the data could grow big: 3x3x400 = 3,600 Effect entities that only exist to have a single relationship each.

2. Create one Effect for each type (damage, confuse, etc) and use a Transformable data type in the Attack entity where I store an array of dictionaries containing each Effect entity identifier (so that they can be found when needed) and the value for that effect. This can be easily handled by NSCoding automatically and would reduce the amount of Entity object from 3,600 to probably 20.

The Effect & Attack entities are rarely accessed (only when the creature is in a battle) and I do not need to search inside them, therefore I think that would not be a noticeable performance impact. I have also read in many websites that they suggest not to store arrays and dictionaries in CoreData. Is there any other way of doing this? and if not, what option would be better?

PS: Sorry for the non descriptive title, I could not figure out what to put.

Answer 1

If you don't plan to change the kinds of your effects you could have an entity that you could call CreatureAttack where each row completely specifies the effects of a creature's attack. The columns might be: foreign key to a Creature , foreign key to an Attack , Damage , Confuse , Poison , etc. For each effect column a row would have a value of the effect for this attack and creature.

This entity will only have at most # Creature x # Attack rows and you can find out everything about a creature's attack by pulling just one row.

Otherwise I think solution 1 is cleaner and the performance hit of having a few thousand rows should be negligible especially if you put an index on the Creature foreign key and/or a compound index on both Creature and Attack foreign keys (supported in iOS5).