我从API获取JSON数据并在对象中解析数据，然后将对象简单地存储在对象数组中。对象本身包含有关报纸文章的数据。但是，我需要过滤该数据。我从JSON获得的一些对象实际上没有文章内容，因为它们是图片而不是文章（即API的JSON中的一些“节点”具有我不希望在我的表视图中看到的内容）
在我的JSON解析函数中，我试图使它只有在“articleContent”变量的字符数大于40时，解析的对象才会被添加到已解析对象的数组中。这就是它看起来像。
if issueElement.articleContent.characters.count > 40 {
self.currentIssueObjects.addObject(issueElement)
}
但是，这根本行不通。我得到典型的“在展开可选值时意外发现的nil”错误消息（我没有得到错误的特定行）。我怎样才能做到这一点？我本质上是试图阻止数组中有空文章内容的对象，因为这会搞砸我的表视图（空单元格，重复项等等）。
这是我的cellForRowAtIndexPath代码和我的JSON解析代码：
override func tableView(tableView: UITableView!, cellForRowAtIndexPath indexPath: NSIndexPath!) -> UITableViewCell {
let row = indexPath.row
guard let cell = tableView.dequeueReusableCellWithIdentifier(CurrentIssueArticlesTableCellIdentifier, forIndexPath: indexPath) as? CurrentIssueArticlesTableViewCell else {
print ("error: currentIssueTableView cell is not of class CurrentIssueArticlesTableViewCell, we will use EditorialsTableViewCell instead")
return tableView.dequeueReusableCellWithIdentifier(CurrentIssueArticlesTableCellIdentifier, forIndexPath: indexPath) as! EditorialsTableViewCell
}
let currentIssueObject = currentIssueObjects.objectAtIndex(indexPath.row) as! IssueElement
let title = currentIssueObject.title ?? ""
let timeStampDateObject = NSDate(timeIntervalSince1970: NSTimeInterval(currentIssueObject.timeStamp))
let timeStampDateString = dateFormatter.stringFromDate(timeStampDateObject) ?? "Date unknown"
if let author = currentIssueObject.author {
cell.currentIssueArticlesAuthorLabel!.font = UIFont.preferredFontForTextStyle(UIFontTextStyleSubheadline)
cell.currentIssueArticlesAuthorLabel!.text = author
}
let issueNumber = currentIssueObject.issueNumber ?? ""
let volumeNumber = currentIssueObject.volumeNumber ?? ""
let articleContent = currentIssueObject.articleContent ?? ""
let nodeID = currentIssueObject.nodeID ?? 0
cell.currentIssueArticlesHeadlineLabel.font = UIFont.preferredFontForTextStyle(UIFontTextStyleHeadline)
cell.currentIssueArticlesHeadlineLabel.text = title
cell.currentIssueArticlesPublishDateLabel.font = UIFont.preferredFontForTextStyle(UIFontTextStyleSubheadline)
cell.currentIssueArticlesPublishDateLabel.text = timeStampDateString
if row == 0 {
cell.userInteractionEnabled = false
let imageURL = (currentIssueObjects.objectAtIndex(row) as! IssueElement).imageURL
cell.currentIssueArticlesHeadlineLabel.textColor = UIColor.clearColor()
cell.currentIssueArticlesAuthorLabel.textColor = UIColor.clearColor()
cell.currentIssueArticlesPublishDateLabel.textColor = UIColor.clearColor()
cell.request?.cancel()
if let image = self.imageCache.objectForKey(imageURL!) as? UIImage {
cell.currentIssueArticlesBackgroundImageView.image = image
} else {
cell.currentIssueArticlesBackgroundImageView.image = UIImage(named: "reveal Image")
cell.request = Alamofire.request(.GET, imageURL!).responseImage() { response in
if response.result.error == nil && response.result.value != nil {
self.imageCache.setObject(response.result.value!, forKey: response.request!.URLString)
cell.currentIssueArticlesBackgroundImageView.image = response.result.value
} else {
}
}
}
cell.currentIssueArticlesBackgroundImageView.hidden = false
}
else {
cell.currentIssueArticlesBackgroundImageView.hidden = true
}
return cell
}
JSON解析代码：
func populateCurrentIssue() {
if populatingCurrentIssue {
return
}
populatingCurrentIssue = true
self.cellLoadingIndicator.backgroundColor = goldenWordsYellow
self.cellLoadingIndicator.startAnimating()
Alamofire.request(GWNetworking.Router.Issue).responseJSON() { response in
if let JSON = response.result.value {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)) {
var nodeIDArray : [Int]
if (JSON .isKindOfClass(NSDictionary)) {
for node in JSON as! Dictionary<String, AnyObject> {
let nodeIDValue = node.0
var lastItem : Int = 0
self.nodeIDArray.addObject(nodeIDValue)
if let issueElement : IssueElement = IssueElement(title: "Could not retrieve title", nodeID: 0, timeStamp: 0, imageURL: "init", author: "Author not found", issueNumber: "Issue # error", volumeNumber: "Volume # error", articleContent: "Could not retrieve article content", coverImageInteger: "init", coverImage: UIImage()) {
issueElement.title = node.1["title"] as! String
issueElement.nodeID = Int(nodeIDValue)!
let timeStampString = node.1["revision_timestamp"] as! String
issueElement.timeStamp = Int(timeStampString)!
issueElement.imageURL = String(node.1["image_url"])
if let author = node.1["author"] as? String {
issueElement.author = author
}
if let issueNumber = node.1["issue_int"] as? String {
issueElement.issueNumber = issueNumber
}
if let volumeNumber = node.1["volume_int"] as? String {
issueElement.volumeNumber = volumeNumber
}
if let articleContent = node.1["html_content"] as? String {
issueElement.articleContent = articleContent
}
issueElement.coverImageInteger = String(node.1["cover_image"]) // addition specific to the Current Issue View Controller
lastItem = self.currentIssueObjects.count
print(issueElement.nodeID)
if issueElement.articleContent.characters.count > 40 {
self.currentIssueObjects.addObject(issueElement)
print(issueElement.nodeID)
}
// Sorting with decreasing timestamp from top to bottom.
let timestampSortDescriptor = NSSortDescriptor(key: "timeStamp", ascending: false)
self.currentIssueObjects.sortUsingDescriptors([timestampSortDescriptor])
// Placing the object with coverImage
let coverImageSortDescriptor = NSSortDescriptor(key: "coverImageInteger", ascending: false)
self.currentIssueObjects.sortUsingDescriptors([coverImageSortDescriptor])
let indexPaths = (lastItem..<self.currentIssueObjects.count).map {
NSIndexPath(forItem: $0, inSection: 0) }
}
}
}
dispatch_async(dispatch_get_main_queue()) {
self.currentIssueTableView.reloadData()
self.cellLoadingIndicator.stopAnimating()
self.cellLoadingIndicator.hidesWhenStopped = true
}
}
}
self.populatingCurrentIssue = false
}
}