问题
How do I add a Fetched Property in XCode's Data Model Editor for minimum value of one attribute??
My model:
Model http://www.freeimagehosting.net/uploads/b48853070e.png
Item (name, note, storedItem)
StoredItem (price, item)
Item 1 ---> N StoredITem (1->N Relationship)
I want that Item has a fetched property named minPrice and its value is the minimum value setted for price in the storedItems.
Example:
Item1 (banana, storedItem1 ... storedItem4, 10)
StoredItem1 (10,item1)
StoredItem2 (15,item1)
StoredItem3 (30,item1)
StoredItem4 (54,item1)
What do I put in Destination?? StoredItem?
Fetched Property in Data Model Editor http://www.freeimagehosting.net/uploads/2a68de007d.png
And what do I put in Expression??
Expression in Data Model Editor http://www.freeimagehosting.net/uploads/766ab9af6f.png
回答1:
The destination is the type of entity you want back.
It sounds like you want a StoredItem back, since that has a price on it.
What I think you want is a fetched property on Item called minPrice, with this expression:
"@min.storedItems.price"
来源：https://stackoverflow.com/questions/2664776/fetched-property-in-xcode-data-model-editor-for-minimum-value