self.tableView.reloadData()在Swift中不起作用

Question

我正在尝试同时学习开发Swift的基础知识iOS,所以请耐心等待.我有一个TableViewController首先解析本地JSON文件并将其非常简单的数据渲染到TableViewCellSectionHeaderViews中.在同一个中TableViewController,我正在调用一个JSON端点,它返回数据,然后我将其设置为变量,这样我就可以访问我实际想要获得的内容(API结构不太理想).所以,我最终设置了正确的数据self.tableData然后调用self.tableView.reloadData()但没有任何反应.是什么赋予了？

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()
        }
    }
}

Answer 1

您需要UI通过以下方式在线程上重新加载表:

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

//swift 5
DispatchQueue.main.async{
    self.tableView.reloadData()
}

跟进:更方便的替代connection.start()方法是使用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,您可能希望通过bytesDownloaded/bytesNeeded计算下载进度

Answer 2

你只需输入:

首先是IBOutlet:

@IBOutlet var appsTableView : UITableView

然后在Action func中:

self.appsTableView.reloadData()

Answer 3

所以，问题是我试图不恰当地使用 @lazy，这导致我的 Business 变量本质上是一个常量，因此不可编辑。另外，我现在只加载从 API 返回的数据，而不是加载本地 json。

import UIKit

class BusinessTableViewController: UITableViewController {

    var data: NSMutableData = NSMutableData()
    var Business: NSMutableArray = NSMutableArray()

    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
    }

    override func tableView(tableView: UITableView?, numberOfRowsInSection section: Int) -> Int {
        if (Business.count > 0) {
            let biz = Business[section] as NSDictionary
            let beers = biz["results"] as NSArray
            return beers.count
        } else {
            return 0;
        }
    }

    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 beers = biz["results"] as NSArray
            let beer = beers[path.row] as NSDictionary

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

        return cell
    }

    override func tableView(tableView: UITableView!, viewForHeaderInSection section: Int) -> UIView! {
        let view = LocationHeaderView()
        let biz = Business[section] as NSDictionary
        if (Business.count > 0) {
            let count = "\(Business.count)"
            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 removed 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 {
            Business = jsonResult
            tableView.reloadData()
        }
    }
}

@lazy 上的 Swift 文档：

您必须始终将惰性属性声明为变量（使用 var 关键字），因为在实例初始化完成之前可能无法检索其初始值。常量属性在初始化完成之前必须始终具有值，因此不能将其声明为惰性属性。