关闭以前的 VC 后仅重新加载新数据
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【中文标题】关闭以前的 VC 后仅重新加载新数据【英文标题】：Reloading only new data after dismissing previous VC 【发布时间】：2019-12-10 20:14:45 【问题描述】：所以我有一个 Photo VC，我可以在其中发布如下所述的图片和标题：
@IBAction func postPressed(_ sender: Any)
self.view.isUserInteractionEnabled = false
if imageOutlet.imageView?.image != UIImage(named: "plus_photo") && postImageTextField.text.count >= 5 && postImageTextField.text != "Write a caption..."
var userProfileImageData = Data()
let query = PFQuery(className: "_User")
query.whereKey("username", equalTo: PFUser.current()?.username)
query.findObjectsInBackground(block: (objects: [PFObject]?,error: Error?) in
if let objects = objects
for object in objects
let userImageFile = object["profilePic"] as? PFFileObject
userImageFile?.getDataInBackground(block: (userProfileImageData1: Data?, error: Error?) in
if error == nil
userProfileImageData = userProfileImageData1!
let currentDateTime = Date()
let formatter = DateFormatter()
formatter.timeStyle = .short
formatter.dateStyle = .none
let captionData = self.postImageTextField.text
let userPhoto = PFObject(className: "PicPost")
let imageData = self.imageOutlet.imageView?.image?.jpegData(compressionQuality: 0.1)!
let imageFile = PFFileObject(name: "image.png", data: imageData!)
let imageFile2 = PFFileObject(name: "image.png", data: userProfileImageData)
userPhoto["ProfilePhoto"] = imageFile2
userPhoto["Bar"] = self.barText
userPhoto["ImageFile"] = imageFile
userPhoto["UserCaption"] = captionData
userPhoto["UserLikes"] = 0
userPhoto["UserTime"] = (formatter.string(from: currentDateTime))
userPhoto["Username"] = PFUser.current()?.username
userPhoto.saveInBackground (success, error) in
if success
self.postImageTextField.resignFirstResponder()
//Go back to original VC
self.presentingViewController?.dismiss(animated: true, completion: nil)
else
print(error)
self.view.isUserInteractionEnabled = true
else
print(error)
)
)
我使用以下代码解散了这个 VC：
self.presentingViewController?.dismiss(animated: true, completion: nil)
这个新的tableView VC已经加载了数据：
func getPicData()
let query = PFQuery(className: "PicPost")
query.whereKey("Bar", equalTo: BarText!)
query.addDescendingOrder("createdAt")
query.limit = picLimit
query.findObjectsInBackground(block: (objects: [PFObject]?,error: Error?) in
if let objects = objects
for object in objects
self.picsLoaded = true
let ImageFile = object["ImageFile"] as? PFFileObject
let urlString = ImageFile?.url as! String
if let url = URL(string: urlString)
let data = try? Data(contentsOf: url)
if let imageData = data
self.picPostPicUrlArray.append(urlString as NSString)
self.picPostPicImageCache.setObject(UIImage(data:imageData)!,forKey: urlString as NSString)
let ProfileImageFile = object["ProfilePhoto"] as? PFFileObject
let urlString2 = ProfileImageFile?.url as! String
if let url2 = URL(string: urlString2)
let data = try? Data(contentsOf: url2)
if let imageData = data
self.picPostProPicUrlArray.append(urlString2 as NSString)
self.picPostProPicImageCache.setObject(UIImage(data: imageData)!, forKey: urlString2 as NSString)
if object["UserLikes"] != nil && object["Username"] != nil && object["UserTime"] != nil
self.picLikeArray.append(object["UserLikes"] as! Int)
self.picUsernameArray.append(object["Username"] as! String)
self.picTimeArray.append(object["UserTime"] as! String)
self.picObjectIdArray.append(object.objectId!)
self.picCaptionArray.append(object["UserCaption"] as! String)
self.Reload()
)
如您所见，函数 getPicData() 已经从 parse.com 加载了所有数据。它存储在各种数组中。
我想做的是只加载新数据并将其添加到当前tableView。我尝试做的是从 PhotoVC 到 tableView VC。然后，新的 segue 将重新加载所有数据（）。不幸的是，这对我的记忆力非常不利。
我需要解决的两个问题：
1) 仅加载新数据并将其加载到当前表视图 2) 关闭 tableView VC 以返回主屏幕。现在它被解散到它刚刚来自的那个，即post VC。
谢谢
【问题讨论】：
【参考方案1】：对于向现有可用数组添加新数据的第一个问题。您可以使用 PhotoVC 中的委托方法将新发布的对象传递给您以前的控制器，即在您的情况下为 tableView VC 。这是两个类之间委托的代码 sn-p。
protocol PhotoVCdelegate : class
func postAdded(item : PFObject)
class PhotoVC
weak var delegate : PhotoVCdelegate?
@IBAction func postPressed(_ sender: Any)
self.view.isUserInteractionEnabled = false
if imageOutlet.imageView?.image != UIImage(named: "plus_photo") && postImageTextField.text.count >= 5 && postImageTextField.text != "Write a caption..."
var userProfileImageData = Data()
let query = PFQuery(className: "_User")
query.whereKey("username", equalTo: PFUser.current()?.username)
query.findObjectsInBackground(block: (objects: [PFObject]?,error: Error?) in
if let objects = objects
for object in objects
let userImageFile = object["profilePic"] as? PFFileObject
userImageFile?.getDataInBackground(block: (userProfileImageData1: Data?, error: Error?) in
if error == nil
userProfileImageData = userProfileImageData1!
let currentDateTime = Date()
let formatter = DateFormatter()
formatter.timeStyle = .short
formatter.dateStyle = .none
let captionData = self.postImageTextField.text
let userPhoto = PFObject(className: "PicPost")
let imageData = self.imageOutlet.imageView?.image?.jpegData(compressionQuality: 0.1)!
let imageFile = PFFileObject(name: "image.png", data: imageData!)
let imageFile2 = PFFileObject(name: "image.png", data: userProfileImageData)
userPhoto["ProfilePhoto"] = imageFile2
userPhoto["Bar"] = self.barText
userPhoto["ImageFile"] = imageFile
userPhoto["UserCaption"] = captionData
userPhoto["UserLikes"] = 0
userPhoto["UserTime"] = (formatter.string(from: currentDateTime))
userPhoto["Username"] = PFUser.current()?.username
userPhoto.saveInBackground (success, error) in
if success
self.postImageTextField.resignFirstResponder()
//Go back to original VC
//HERE you can pass this information to your controller
self.delegate?.postAdded(item : userPhoto)
self.presentingViewController?.dismiss(animated: true, completion: nil)
else
print(error)
self.view.isUserInteractionEnabled = true
else
print(error)
)
)
在您的 TableViewVC.swift 中 假设您具有在按钮单击时呈现控制器的功能。
class TableViewVC
@IBAction func createPostBtnPressed(_ sender: Any)
if let vc = self.storyboard?.instantiateViewController(withIdentifier:"PhotoVC") as? PhotoVC
vc.delegate = self
self.presentViewController(vc, animated: true, completion: nil)
上传数据成功后会调用 PhotoVC 的委托方法。
extension TableViewVC : PhotoVCdelegate
func postAdded(item : PFObject)
// append required value from item object into your arrays and reload tableview .
希望这会有所帮助！
【讨论】：
我有一个问题。当我将新图像设置到图像缓存时，它会将其添加到末尾。所以现在 imageCache 在 tableview 的最后一个而不是第一个显示最新的图像。 为什么要将图像保存在本地数据库中。将图片网址保存在您的最后。在 table view 的每个 cellfor_rowatindexpath 委托方法上获取这些图像。使用翠鸟库 (github.com/onevcat/Kingfisher) 。它会自动为给定的 url 保存图像。以上是关于关闭以前的 VC 后仅重新加载新数据的主要内容，如果未能解决你的问题，请参考以下文章
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