viewView数据源在viewDidLoad()中为空 - Swift [英] tableView data source empty in viewDidLoad() - Swift
问题描述
下面是我的ViewController代码。 GetRequest中的println打印从HTTP GET请求接收的正确数据。此时,tableData有10个键值对。但是,如果我在viewDidLoad()中调用GetRequest()之后设置了一个断点,则tableData为空并且tableView中不显示任何内容。为什么是这样?我哪里错了?
Below is my ViewController code. The println in GetRequest prints the correct data that it receives from the HTTP GET request. At this point, tableData has 10 key-value pairs. However, if I put a break point after the call to GetRequest() in viewDidLoad(), tableData is empty and nothing is displayed in the tableView. Why is this? Where am I going wrong?
import UIKit
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource
{
@IBOutlet var tableView: UITableView!
var tableData: [String:String] = [:]
let textCellIdentifier = "TextCell"
func GetRequest(urlPath: String)
{
var LatestWaitTimes: [String:String] = [:]
let url: NSURL = NSURL(string: urlPath)!
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithURL(url, completionHandler: {data, response, error -> Void in
if error != nil {
// If there is an error in the web request, print it to the console
println(error.localizedDescription)
}
var err: NSError?
var jsonResult: AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: &err)
if err != nil {
// If there is an error parsing JSON, print it to the console
println("JSON Error \(err!.localizedDescription)")
}
let json = JSON(jsonResult!)
let count: Int? = json.array?.count
if let ct = count {
for index in 0...ct-1 {
let name = json[index]["CrossingName"].string
var wait = json[index]["WaitTime"].stringValue
if (wait == "-1")
{
wait = "No Info"
}
else
{
wait += " min"
}
println(name!+": "+wait)
LatestWaitTimes[json[index]["CrossingName"].stringValue] = wait as String?
}
}
self.tableData = LatestWaitTimes
})
task.resume()
}
override func viewDidLoad() {
super.viewDidLoad()
var apiInfo = GetWaitTimes()
GetRequest(apiInfo.BorderCrossingApi+"?AccessCode="+apiInfo.AccessCode)
self.tableView.delegate = self
self.tableView.dataSource = self
tableView.reloadData()
}
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return 1;
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return tableData.count
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
var cell = tableView.dequeueReusableCellWithIdentifier(self.textCellIdentifier) as! UITableViewCell
let thisEntry = self.tableData.values.array[indexPath.row]
cell.textLabel?.text = thisEntry+": "+tableData[thisEntry]!
return cell
}
func tableView(tableView: UITableView, didDeselectRowAtIndexPath indexPath: NSIndexPath) {
tableView.deselectRowAtIndexPath(indexPath, animated: true)
}
}
推荐答案
问题是 GetRequest
以异步方式运行。所以你必须在 completionHandler
的 dataTaskWithURL
中 reloadData
:
The problem is that GetRequest
runs asynchronously. So you have to reloadData
inside the completionHandler
of dataTaskWithURL
:
let task = session.dataTaskWithURL(url, completionHandler: {data, response, error -> Void in
// do all of your existing stuff here
dispatch_async(dispatch_get_main_queue()) {
self.tableData = LatestWaitTimes
self.tableView.reloadData()
}
})
task.resume()
你可以删除来自 viewDidLoad
中的 reloadData
。
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