core-data

问题 I have a small Core Data Model which stores an array of Strings (search history). When fetching the Data I'd like to sort by the time created. I currently just have one property in my model called searchHistory is there a way I can use the following code (key: to sort the data or will I need to add a time saved to the model? let request = NSFetchRequest<NSFetchRequestResult>(entityName: entityName) request.sortDescriptors = [NSSortDescriptor.init(key: "", ascending: true)] 回答1: Yes, you need

问题 I have a small Core Data Model which stores an array of Strings (search history). When fetching the Data I'd like to sort by the time created. I currently just have one property in my model called searchHistory is there a way I can use the following code (key: to sort the data or will I need to add a time saved to the model? let request = NSFetchRequest<NSFetchRequestResult>(entityName: entityName) request.sortDescriptors = [NSSortDescriptor.init(key: "", ascending: true)] 回答1: Yes, you need

问题 In XCode 12, if I create a new SwiftUI App and check the "Use Core Data" button, the resulting application (with no changes) shows a blank screen in simulator (as well as on a device). In preview it shows the example timestamps as expected. Why are the simulator/device not showing the example timestamps? 回答1: If you want to see the sample inputs from the template (10 rows with timestamp) in your simulator, you need to change in App.swift: let persistenceController = PersistenceController

问题 When I create models in core data, I'm always a little perplexed by which integer type I should choose—16, 32, 64. I'm almost always needing something for a simple, basic number: a count of people in the household, for my present case. Probably going to be a number between 1-20. Or, I have an incrementing case id number in another instance...can't imagine that going further than few hundred people. And here's the deal...It's clear that true computer science folk think of numbers differently,

问题 When I create models in core data, I'm always a little perplexed by which integer type I should choose—16, 32, 64. I'm almost always needing something for a simple, basic number: a count of people in the household, for my present case. Probably going to be a number between 1-20. Or, I have an incrementing case id number in another instance...can't imagine that going further than few hundred people. And here's the deal...It's clear that true computer science folk think of numbers differently,

问题 When I create models in core data, I'm always a little perplexed by which integer type I should choose—16, 32, 64. I'm almost always needing something for a simple, basic number: a count of people in the household, for my present case. Probably going to be a number between 1-20. Or, I have an incrementing case id number in another instance...can't imagine that going further than few hundred people. And here's the deal...It's clear that true computer science folk think of numbers differently,

问题 When I create models in core data, I'm always a little perplexed by which integer type I should choose—16, 32, 64. I'm almost always needing something for a simple, basic number: a count of people in the household, for my present case. Probably going to be a number between 1-20. Or, I have an incrementing case id number in another instance...can't imagine that going further than few hundred people. And here's the deal...It's clear that true computer science folk think of numbers differently,

问题 I have an array of ids. I want to fetch core data entity for the items in the ids array. How can we implement that using NSFetchRequest ? 回答1: Use NSPredicate fetchRequest.predicate = NSPredicate(format: "itemId IN %@", itemIds) Instead of itemId set your actual id property name. Now perform a fetch with this fetch request 回答2: let hrData = self.cstProjectDetails as NSArray 来源： https://stackoverflow.com/questions/51264432/how-to-fetch-array-of-objects-using-array-of-ids-using-core-data

问题 In my app I store data with core data. Recently I discovered the new feature introduced by Apple in WWDC19 which allows core data to work with CloudKit. I just enabled cloudKit for my app and used an NSPersistentCloudKitContainer instead of NSPersistentContainer and all was set up ! All my data is shared between ios devices. That works like NSPersistentContainer but it sends a copy of changes on icloud server, so there is always a local cache of data. Now I'd like to access that data from my

问题 I have an app that allows users to save favorites. I am using Core Data to store the favorites as managed objects. I have written some code to prevent the possibility of storing duplicates, but am wondering if there is a better way to do so. Each favorite object has an ID field that is unique. In the following code I am simply looping through and checking the ID field, and if the value already exists, setting a flag value to true, and breaking out of the loop. -(BOOL)addFavorite{ BOOL