UITableView in swift - swift

Question

can anyone tell me what's wrong with my code i always get the same data repeated in all cells
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
cell.textLabel!.textColor = UIColor.whiteColor()
let query = PFQuery(className:"book")
query.findObjectsInBackgroundWithBlock {
(objects: [PFObject]?, error: NSError?) -> Void in
var contentString:String = String()
if error == nil {
print("Success retrieved \(objects!.count) scores.")
if let objects = objects {
for object in objects {
let a:String = object.objectForKey("title") as! String
contentString = a
}
}
cell.textLabel!.text = contentString
}}
return cell
}

Answer 1

It will be better to query all your data into viewDidLoad() or any life cycle you would like.
var contentString = [String]() //<-- use an array of string instead of a string variable
override func viewDidLoad()
{
super.viewDidLoad()
let query = PFQuery(className:"book"){ query.findObjectsInBackgroundWithBlock {
(objects: [PFObject]?, error: NSError?) -> Void in
if error == nil {
print("Success retrieved \(objects!.count) scores.")
if let objects = objects {
for object in objects
{
let value = object["title"] as! String
self.contentString.append(value) //<-- save the query value to your array
}
self.tableView.reloadData() //<--- then you reload your UI
}
}}
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell
{
let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
cell.textLabel!.textColor = UIColor.whiteColor()
cell.textLabel!.text = self.contentString[indexPath.row] //<-- then assign the value into your cell
return cell
}

Answer 2

content inside your loop should be like this.
let a:String = object.objectForKey("title") as! String
contentString += a
and i noticed your block calls for same query always. can you tell me whats the different there
query.findObjectsInBackgroundWithBlock {
(objects: [PFObject]?, error: NSError?) -> Void in
var contentString:String = String()
if error == nil {
print("Success retrieved \(objects!.count) scores.")
if let objects = objects {
for object in objects {
let a:String = object.objectForKey("title") as! String
contentString = a
}
}
cell.textLabel!.text = contentString
}}

Answer 3

The query in cellForRowAtIndex is trouble. Imagine, every time a cell comes into view, the code asks for every book from the server.
Put the query outside the datasource method (viewWillAppear, for example). When the query is complete, initialize an array property with the results (e.g. self.bookObjects = objects).
Then in cellForRowAtIndex...
let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
cell.textLabel!.textColor = UIColor.whiteColor()
// this is the important idea...
let object = self.bookObjects[indexPath.row]
let a:String = object.objectForKey("title") as! String
cell.textLabel!.text = a
return cell