self.tableView.reloadData（）在Swift中不起作用 [英] self.tableView.reloadData() not working in Swift

问题描述

我正在尝试学习 Swift &同时， iOS dev的基础知识，所以请耐心等待。我有一个 TableViewController ，它首先解析一个本地的 JSON 文件并将其非常简单的数据呈现到 TableViewCell 和SectionHeaderViews。在同一个 TableViewController 中，我正在调用 JSON 端点，它返回数据，我是然后设置变量，这样我就可以访问我真正想要的东西（API结构不太理想）。所以，我最终将正确的数据设置为 self.tableData ，然后调用 self.tableView.reloadData（）但是什么都没发生。给出了什么？

I'm attempting to learn Swift & the basics of iOS dev at the same time, so bear with me. I've got a TableViewController that is firstly parsing a local JSON file and rendering it's very simple data into TableViewCell and SectionHeaderViews. Within the same TableViewController, I'm making a call to a JSON endpoint, which is returning data, which I am then setting to variables so I can access what I actually want to get at (the API structure is less than desirable). So, I finally set the proper data to be self.tableData and then call self.tableView.reloadData() but nothing happens. What gives?

import UIKit

class BusinessTableViewController: UITableViewController {

    var data: NSMutableData = NSMutableData()
    var tableData: NSArray = NSArray()

    @lazy var Business: NSArray = {
        let pathTCT = NSBundle.mainBundle().pathForResource("TCT", ofType: "json")
        let data = NSData.dataWithContentsOfFile(pathTCT, options: nil, error: nil)
        return NSJSONSerialization.JSONObjectWithData(data, options: nil, error: nil) as NSArray
        }()

    override func viewDidLoad() {
        super.viewDidLoad()

        navigationItem.titleView = UIImageView(image: UIImage(named: "growler"))

        tableView.registerClass(BeerTableViewCell.self, forCellReuseIdentifier: "cell")
        tableView.separatorStyle = .None

        fetchKimono()
    }

    override func numberOfSectionsInTableView(tableView: UITableView!) -> Int {
//        return Business.count
        return 1
    }

    override func tableView(tableView: UITableView?, numberOfRowsInSection section: Int) -> Int {
        let biz = Business[section] as NSDictionary
        let results = biz["results"] as NSDictionary
        let beers = results["collection1"] as NSArray
        return beers.count
    }

    override func tableView(tableView: UITableView?, cellForRowAtIndexPath indexPath: NSIndexPath?) -> UITableViewCell? {
        let cell = tableView!.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath!) as BeerTableViewCell
        if let path = indexPath {
            let biz = Business[path.section] as NSDictionary
            let results = biz["results"] as NSDictionary
            let beers = results["collection1"] as NSArray
            let beer = beers[path.row] as NSDictionary

            cell.titleLabel.text = beer["BeerName"] as String
        }

        return cell
    }

    override func tableView(tableView: UITableView!, titleForHeaderInSection section: Int) -> String! {
        let biz = Business[section] as NSDictionary
        return biz["name"] as String
    }

    override func tableView(tableView: UITableView!, viewForHeaderInSection section: Int) -> UIView! {
        let biz = Business[section] as NSDictionary
        let view = LocationHeaderView()
        view.titleLabel.text = (biz["name"] as String).uppercaseString
        return view
    }

    override func tableView(tableView: UITableView!, heightForHeaderInSection section: Int) -> CGFloat {
        return 45
    }

    func fetchKimono() {
        var urlPath = "names have been changed to protect the innocent"
        var url: NSURL = NSURL(string: urlPath)
        var request: NSURLRequest = NSURLRequest(URL: url)
        var connection: NSURLConnection = NSURLConnection(request: request, delegate: self, startImmediately: false)

        connection.start()
    }

    func connection(didReceiveResponse: NSURLConnection!, didReceiveResponse response: NSURLResponse!) {
        // Recieved a new request, clear out the data object
        self.data = NSMutableData()
    }

    func connection(connection: NSURLConnection!, didReceiveData data: NSData!) {
        // Append the recieved chunk of data to our data object
        self.data.appendData(data)
    }

    func connectionDidFinishLoading(connection: NSURLConnection!) {
        // Request complete, self.data should now hold the resulting info
        // Convert the retrieved data in to an object through JSON deserialization
        var err: NSError
        var jsonResult: NSDictionary = NSJSONSerialization.JSONObjectWithData(data, options:    NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary
        var results: NSDictionary = jsonResult["results"] as NSDictionary
        var collection: NSArray = results["collection1"] as NSArray
        if jsonResult.count>0 && collection.count>0 {
            var results: NSArray = collection as NSArray
            self.tableData = results
            self.tableView.reloadData()
        }
    }
}

推荐答案

您需要重新加载表格在 UI 主题通过：

You'll need to reload the table on the UI thread via:

//swift 2.3
dispatch_async(dispatch_get_main_queue(), { () -> Void in
    self.tableView.reloadData()
})

//swift 3
DispatchQueue.main.async{
    self.tableView.reloadData()
}

关注up：
替代 connection.start（）的方法是使用 NSURLConnection.sendAsynchronousRequest（...）

Follow up: An easier alternative to the connection.start() approach is to instead use NSURLConnection.sendAsynchronousRequest(...)

//NSOperationQueue.mainQueue() is the main thread
NSURLConnection.sendAsynchronousRequest(NSURLRequest(URL: url), queue: NSOperationQueue.mainQueue()) { (response, data, error) -> Void in
    //check error
    var jsonError: NSError?
    let json: AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.allZeros, error: &jsonError)
    //check jsonError
    self.collectionView?.reloadData()
}

这不允许您灵活地跟踪字节，例如您可能想要通过以下方式计算下载进度bytesDownloaded / bytesNeeded

This doesn't allow you the flexibility of tracking the bytes though, for example you might want to calculate the progress of the download via bytesDownloaded/bytesNeeded

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