从 EKEventStore 获取事件并在 Swift iOS8 中的 tableView 中显示

Question

我正在尝试创建一个小型应用程序，它将获取所有事件并将它们显示在 tableView 中。

我的具体问题是：

1. 我的fetchEvents() 方法是否正确实现？
2. 我应该在哪里调用fetchEvent() 方法以便在应用打开时显示列表（是否在viewDidLoad 中？）并在添加/编辑新事件后刷新它？

谢谢！

这是MasterViewController.swift 文件的代码：

import UIKit
import EventKitUI

class MasterViewController: UITableViewController , EKEventEditViewDelegate{

var objects = NSMutableArray()
let eventStore =  EKEventStore()


override func awakeFromNib() {
    super.awakeFromNib()
}

override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view, typically from a nib.
    self.navigationItem.leftBarButtonItem = self.editButtonItem()

    let addButton = UIBarButtonItem(barButtonSystemItem: .Add, target: self, action: "insertNewObject:")
    self.navigationItem.rightBarButtonItem = addButton

    //self.fetchEvents()
}

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

func insertNewObject(sender: AnyObject) {

    let controller = EKEventEditViewController()

    eventStore.requestAccessToEntityType(EKEntityType(), completion: {granted, error in })
    controller.eventStore = eventStore

    controller.editViewDelegate = self
    self.presentModalViewController(controller, animated: true)


    let indexPath = NSIndexPath(forRow: 0, inSection: 0)
    self.tableView.insertRowsAtIndexPaths([indexPath], withRowAnimation: .Automatic)
}

func eventEditViewController(controller: EKEventEditViewController!, didCompleteWithAction action: EKEventEditViewAction) {
    self.dismissModalViewControllerAnimated(true)
}

func fetchEvents() -> NSMutableArray {

    eventStore.requestAccessToEntityType(EKEntityType(), completion: {granted, error in })

    let endDate = NSDate(timeIntervalSinceNow: 604800*10);   //This is 10 weeks in seconds
    let predicate = self.eventStore.predicateForEventsWithStartDate(NSDate(), endDate: NSDate(), calendars: nil)

    var events = NSMutableArray(array: self.eventStore.eventsMatchingPredicate(predicate))

    return events

    /*
    var indexes = NSMutableIndexSet(index: 5)

    indexes.addIndex(4)

    objects.insertObjects(events, atIndexes: indexes) */

    // Create the start date components



   /* NSDateComponents *oneDayAgoComponents = [[NSDateComponents alloc] init];
    oneDayAgoComponents.day = -1;

    let oneDayAgo = currentCalendar.date dateByAddingComponents:oneDayAgoComponents*/

}

// #pragma mark - Segues

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "showDetail" {
        let indexPath = self.tableView.indexPathForSelectedRow()
        let object = objects[indexPath.row] as NSDate
        (segue.destinationViewController as DetailViewController).detailItem = object
    }
}

// #pragma mark - Table View

override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    return 1
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return objects.count
}

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell

    let object = objects[indexPath.row] as NSDate
    cell.textLabel.text = object.description
    return cell
}

override func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool {
    // Return false if you do not want the specified item to be editable.
    return true
}

override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
    if editingStyle == .Delete {
        objects.removeObjectAtIndex(indexPath.row)
        tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
    } else if editingStyle == .Insert {
        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view.
    }
}
}

Answer 1

首先，您应该在fetchEvents 回调函数中为eventStore.requestAccessToEntityType 完成其余的工作：

func fetchEvents() -> NSMutableArray {
    eventStore.requestAccessToEntityType(EKEntityType()) completion: {
        granted, error in
        ... the rest of the code ...
    })
}

当然现在它是异步的，你需要在回调中返回数据而不是返回它：

func fetchEvents(completed: (NSMutableArray) -> ()) {
    eventStore.requestAccessToEntityType(EKEntityType()) completion: {
        granted, error in
        let endDate = NSDate(timeIntervalSinceNow: 604800*10);   //This is 10 weeks in seconds
        let predicate = self.eventStore.predicateForEventsWithStartDate(NSDate(), endDate: NSDate(), calendars: nil)
        let events = NSMutableArray(array: self.eventStore.eventsMatchingPredicate(predicate))
        completed(events)
    })
}

但是现在您遇到了另一个问题...您在闭包中使用了 self ，从而捕获了一个引用，这可能导致“reference cycle”。在这种特殊情况下，我很确定这不会发生，因为 requestAccessToEntityType() 不会保留对您的闭包的引用（我非常确定），但使用它是一个好主意[weak self] 每当您在回调函数中使用 self 时：

一旦你这样做了，self 是一个可选的，所以你需要确保它不是 nil…

func fetchEvents(completed: (NSMutableArray) -> ()) {
    eventStore.requestAccessToEntityType(EKEntityType()) completion: { [weak self]
        granted, error in
        if let strongSelf = self {
            let endDate = NSDate(timeIntervalSinceNow: 604800*10);   //This is 10 weeks in seconds
            let predicate = strongSelf.eventStore.predicateForEventsWithStartDate(NSDate(), endDate: NSDate(), calendars: nil)
            let events = NSMutableArray(array: strongSelf.eventStore.eventsMatchingPredicate(predicate))
            completed(events)
        }
    })
}

但仔细观察，我们从不使用self，只使用self.eventStore，因此我们可以直接捕获对它的弱引用：

func fetchEvents(completed: (NSMutableArray) -> ()) {
    eventStore.requestAccessToEntityType(EKEntityType()) completion: { [weak weakEventStore = self.eventStore]
        granted, error in
        if let eventStore = weakEventStore {
            let endDate = NSDate(timeIntervalSinceNow: 604800*10);   //This is 10 weeks in seconds
            let predicate = eventStore.predicateForEventsWithStartDate(NSDate(), endDate: NSDate(), calendars: nil)
            let events = NSMutableArray(array: eventStore.eventsMatchingPredicate(predicate))
            completed(events)
        }
    })
}

最后，你真的应该检查错误而不是忽略它们，（granted 可能是假的，这意味着用户没有给你访问权限，或者可能有错误（所以你需要检查 @ 987654335@ 为零 (if error { /* handle failure */ })

PS - 我有working code which uses event kit on github，您可能会觉得有用。