获取要用于图表的核心数据

Posted 2023-02-26

【中文标题】获取要用于图表的核心数据

【英文标题】：Fetching Core Data to use for a chart

【发布时间】：2016-08-22 02:21:25

【问题描述】：

是否有任何将 Core Data 用于图表的示例？我一直在尝试示例项目，但没有成功。我了解如何在声明数组时使用数据，但在使用获取的结果时会很困难。

这是我找到的图表视图示例：

var chartLegend = ["11-14", "11-15", "11-16", "11-17", "11-18", "11-19", "11-20"]
var chartData = [70, 80, 76, 88, 90, 69, 74]

func numberOfBarsInBarChartView(barChartView: JBBarChartView!) -> UInt 
    return UInt(chartData.count)


func barChartView(barChartView: JBBarChartView!, heightForBarViewAtIndex index: UInt) -> CGFloat 
    return CGFloat(chartData[Int(index)])


func barChartView(barChartView: JBBarChartView!, colorForBarViewAtIndex index: UInt) -> UIColor! 
    return (index % 2 == 0) ? UIColor.lightGrayColor() : UIColor.whiteColor()


func barChartView(barChartView: JBBarChartView!, didSelectBarAtIndex index: UInt) 
    let data = chartData[Int(index)]
    let key = chartLegend[Int(index)]

    infoLabel.text = "Weather on \(key): \(data)"


func didDeselectBarChartView(barChartView: JBBarChartView!) 
    infoLabel.text = ""

这是我用于获取数据的内容：

let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext

var fetchedResultController: NSFetchedResultsController = NSFetchedResultsController()


func getFetchedResultController() -> NSFetchedResultsController 
    fetchedResultController = NSFetchedResultsController(fetchRequest: taskFetchRequest(), managedObjectContext: managedObjectContext, sectionNameKeyPath: nil, cacheName: nil)
    return fetchedResultController


func taskFetchRequest() -> NSFetchRequest 
    let fetchRequest = NSFetchRequest(entityName: "Entity")
    let timeSortDescriptor = NSSortDescriptor(key: "attribute1",
                                              ascending: true, selector: #selector(NSString.caseInsensitiveCompare(_:)))
    let milesSortDescriptor = NSSortDescriptor(key: "attribute2",
                                               ascending: true, selector: #selector(NSString.caseInsensitiveCompare(_:)))

    fetchRequest.sortDescriptors = [timeSortDescriptor, milesSortDescriptor]

    return fetchRequest

这就是我能够检索核心数据并将其用于在表格中查看的方式。它如何用于在图表中查看？

 let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext

var fetchedResultController: NSFetchedResultsController = NSFetchedResultsController()

override func viewDidLoad() 
    super.viewDidLoad()
    fetchedResultController = getFetchedResultController()
    fetchedResultController.delegate = self
    do 
        try fetchedResultController.performFetch()
     catch _ 
    
  


// MARK:- Retrieve Tasks

func getFetchedResultController() -> NSFetchedResultsController 
    fetchedResultController = NSFetchedResultsController(fetchRequest: taskFetchRequest(), managedObjectContext: managedObjectContext, sectionNameKeyPath: nil, cacheName: nil)
    return fetchedResultController


func taskFetchRequest() -> NSFetchRequest 
    let fetchRequest = NSFetchRequest(entityName: "RunTime")
    let timeSortDescriptor = NSSortDescriptor(key: "time",
                                                  ascending: true, selector: #selector(NSString.caseInsensitiveCompare(_:)))
    let milesSortDescriptor = NSSortDescriptor(key: "miles",
                                                   ascending: true, selector: #selector(NSString.caseInsensitiveCompare(_:)))

    fetchRequest.sortDescriptors = [timeSortDescriptor, milesSortDescriptor]

    return fetchRequest


override func didReceiveMemoryWarning() 
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.


// MARK: - TableView data source

override func numberOfSectionsInTableView(tableView: UITableView) -> Int 
    let numberOfSections = fetchedResultController.sections?.count
    return numberOfSections!


override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int 
    let numberOfRowsInSection = fetchedResultController.sections?[section].numberOfObjects
    return numberOfRowsInSection!


override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell 

    let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath)
    let runtime = fetchedResultController.objectAtIndexPath(indexPath) as! RunTime
    cell.textLabel?.text = runtime.time
    cell.detailTextLabel!.text = runtime.miles

    return cell


// MARK: - TableView Deleteƒ

override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) 
    let managedObject:NSManagedObject = fetchedResultController.objectAtIndexPath(indexPath) as! NSManagedObject
    managedObjectContext.deleteObject(managedObject)
    do 
        try managedObjectContext.save()
     catch _ 
    


// MARK: - TableView Refresh

func controllerDidChangeContent(controller: NSFetchedResultsController) 
    tableView.reloadData()

【问题讨论】：

您是否创建了自己的实体并生成了相应的 swift 文件？您将数据保存在哪里？

是的，我创建了自己的实体。在上面，我编辑了我的帖子并添加了我在 tableview 中检索核心数据所做的工作

【参考方案1】：

在 ios 13 上使用 SwiftUI，现在使用 @FetchRequest 属性包装器应该非常容易。