试图用解析制作笔记应用程序

Question

我试图制作一个笔记应用程序，所有内容都正确运行但是在我保存笔记但桌面视图为空之后。

我写的所有笔记都会弹出一瞬间消失，并且笔记显示在解析数据库中。

//
//  MasterTableViewController.swift
//  Notes
//
//  Created by uLife on 6/17/15.
//  Copyright (c) 2015 uLife. All rights reserved.


import UIKit

class MasterTableViewController: UITableViewController, PFLogInViewControllerDelegate, PFSignUpViewControllerDelegate {

var noteObjects: NSMutableArray! = NSMutableArray()

override func viewDidLoad() {
    super.viewDidLoad()

    // Uncomment the following line to preserve selection between presentations
    // self.clearsSelectionOnViewWillAppear = false

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem()
}

override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)

    if (PFUser.currentUser() == nil) {



    }else {

        self.fetchAllObjectsFromLocalDatastore()
        self.fetchAllObjects()

    }

}

func fetchAllObjectsFromLocalDatastore() {

    var query: PFQuery = PFQuery(className: "Note")

    query.fromLocalDatastore()

    query.whereKey("username", equalTo: PFUser.currentUser()!.username!)

    query.findObjectsInBackgroundWithBlock { (objects, error) -> Void in

        if (error == nil) {

            var temp: NSArray = objects!; NSArray.self

            self.noteObjects = temp.mutableCopy() as! NSMutableArray

            self.tableView.reloadData()

        }else {

            println(error!.userInfo)

        }

    }

}

func fetchAllObjects() {

    PFObject.unpinAllObjectsInBackgroundWithBlock(nil)

    var query: PFQuery = PFQuery(className: "Note")

    query.whereKey("username", equalTo: PFUser.currentUser()!.username!)

    query.findObjectsInBackgroundWithBlock { (objects, error) -> Void in

        if (error == nil) {

            PFObject.pinAllInBackground(objects, block: nil)

            self.fetchAllObjectsFromLocalDatastore()

        }else {

            println(error!.userInfo)

        }

    }

}

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

// MARK: - Parse Login

    // MARK: - Table view data source

override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    // #warning Potentially incomplete method implementation.
    // Return the number of sections.
    return 1
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    // #warning Incomplete method implementation.
    // Return the number of rows in the section.
    return self.noteObjects.count
}

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


    var object: PFObject = self.noteObjects.objectAtIndex(indexPath.row) as! PFObject

    cell.masterTitleLabel?.text = object["title"] as? String
    cell.masterTextLabel?.text = object["text"] as? String

    return cell
}

override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {

    self.performSegueWithIdentifier("editNote", sender: self)

}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {


    var upcoming: AddNoteTableViewController = segue.destinationViewController as! AddNoteTableViewController

    if (segue.identifier == "editNote") {

        let indexPath = self.tableView.indexPathForSelectedRow()!

        var object: PFObject = self.noteObjects.objectAtIndex(indexPath.row) as! PFObject

        upcoming.object = object

        self.tableView.deselectRowAtIndexPath(indexPath, animated: true)

    }

}

}

Answer 1

我认为你的问题就在这里。 pinAllInBackground是异步方法，因此fetchAllObjectsFromLocalDatastore将立即执行，显然当时本地数据存储中没有对象。

PFObject.pinAllInBackground(objects, block: nil)

self.fetchAllObjectsFromLocalDatastore()

那你需要做什么？实施PFBooleanResultBlock。

PFObject.pinAllInBackground(objects, block: { (success, error) in 
  if error == nil {
    self.fetchAllObjectsFromLocalDatastore()
  }
})