Question

所以我有两个实体。列表和评论。列表可以包含多个相关注释。

extension Listing {

    @NSManaged var listingTitle: String?
    @NSManaged var comments: NSSet?
    @NSManaged var listingLatitude: Double
    @NSManaged var listingLongitude: Double
}

extension Comment {

    @NSManaged var comment: String?
    @NSManaged var commentId: String?
    @NSManaged var rating: Int32
    @NSManaged var username: String?
    @NSManaged var listing: Listing?

}

使用NSPredicate我可以相当轻松地过滤出位于特定地理区域的商家信息。

// Fetching data from CoreData
            let fetchRequest = NSFetchRequest()
            fetchRequest.predicate = NSPredicate(format: "listingLatitude BETWEEN {%f,%f} AND listingLongitude BETWEEN {%f,%f}", (latitude-0.10), (latitude+0.10), (longitude-0.10), (longitude+0.10))
            let entity = NSEntityDescription.entityForName("Listing", inManagedObjectContext: self.mainMoc)
            fetchRequest.entity = entity

            fetchRequest.sortDescriptors = [sortDescriptor]

            do {
                listings = try self.mainMoc.executeFetchRequest(fetchRequest) as! [Listing]

            }

这样可以正常工作，但是如何使用具有特定评级的评论来过滤掉所有列表？

Answer 1

由于comments是to-Many关系，因此您需要帮助CoreData解决您关注的问题：ALL，ANY或NONE。例如：

fetchRequest.predicate = NSPredicate(format: "ANY comments.rating > 4")

仅包含Listings Comments的任何fetchRequest.predicate = NSPredicate(format: "ALL comments.rating < 2")评分为4或更高，而：

Comments

仅当所有.split()的评分均小于2时，

才会包含它们。

使用fetchrequest谓词过滤掉某些coredata项。

1 个答案: