Filter result from parse query - ios

Question

Hi Im developing a chat app with parse and I have one group-chat tab. What I would like to accomplish Is that when the user registers he/she can choose from a list of "tags" for example, "cats", "dogs" and "cars". Then when the user is signed in the groups tab only shows group-chats associated to the chosen tags. Right now i have a function where the user can create a group-chat but If possible i want to remove that and use my idea that I explained above.
Here's my code for the group's tab:
import UIKit
// Parse loaded from SwiftParseChat-Bridging-Header.h
class GroupsViewController: UITableViewController, UIAlertViewDelegate {
var groups: [PFObject]! = []
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
if PFUser.currentUser() != nil {
self.loadGroups()
}
else {
Utilities.loginUser(self)
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func loadGroups() {
var query = PFQuery(className: PF_GROUPS_CLASS_NAME)
query.findObjectsInBackgroundWithBlock {
(objects: [AnyObject]!, error: NSError!) in
if error == nil {
self.groups.removeAll()
self.groups.extend(objects as [PFObject]!)
self.tableView.reloadData()
} else {
ProgressHUD.showError("Network error")
println(error)
}
}
}
#IBAction func newButtonPressed(sender: UIBarButtonItem) {
self.actionNew()
}
func actionNew() {
var alert = UIAlertView(title: "Please enter a name for your group", message: "", delegate: self, cancelButtonTitle: "Cancel", otherButtonTitles: "OK")
alert.alertViewStyle = UIAlertViewStyle.PlainTextInput
alert.show()
}
func alertView(alertView: UIAlertView, clickedButtonAtIndex buttonIndex: Int) {
if buttonIndex != alertView.cancelButtonIndex {
var textField = alertView.textFieldAtIndex(0);
if let text = textField!.text {
if countElements(text) > 0 {
var object = PFObject(className: PF_GROUPS_CLASS_NAME)
object[PF_GROUPS_NAME] = text
object.saveInBackgroundWithBlock({ (success: Bool, error: NSError!) -> Void in
if success {
self.loadGroups()
} else {
ProgressHUD.showError("Network error")
println(error)
}
})
}
}
}
}
// MARK: - TableView Data Source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.groups.count
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
var cell = tableView.dequeueReusableCellWithIdentifier("cell") as UITableViewCell
var group = self.groups[indexPath.row]
cell.textLabel?.text = group[PF_GROUPS_NAME] as? String
var query = PFQuery(className: PF_CHAT_CLASS_NAME)
query.whereKey(PF_CHAT_GROUPID, equalTo: group.objectId)
query.orderByDescending(PF_CHAT_CREATEDAT)
query.limit = 1000
query.findObjectsInBackgroundWithBlock { (objects: [AnyObject]!, error: NSError!) -> Void in
if let chat = objects.first as? PFObject {
let date = NSDate()
let seconds = date.timeIntervalSinceDate(chat.createdAt)
let elapsed = Utilities.timeElapsed(seconds);
let countString = (objects.count > 1) ? "\(objects.count) meddelanden" : "\(objects.count) meddelande"
cell.detailTextLabel?.text = "\(countString) \(elapsed)"
} else {
cell.detailTextLabel?.text = "0 meddelanden"
}
cell.detailTextLabel?.textColor = UIColor.lightGrayColor()
}
return cell
}
// MARK: - TableView Delegate
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
tableView.deselectRowAtIndexPath(indexPath, animated: true)
var group = self.groups[indexPath.row]
let groupId = group.objectId as String
Messages.createMessageItem(PFUser(), groupId: groupId, description: group[PF_GROUPS_NAME] as String)
self.performSegueWithIdentifier("groupChatSegue", sender: groupId)
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "groupChatSegue" {
let chatVC = segue.destinationViewController as ChatViewController
chatVC.hidesBottomBarWhenPushed = true
let groupId = sender as String
chatVC.groupId = groupId
}
}
}

Answer 1

It sounds like you want to query a class (the one containing chats) with the constraint that an array column property of that class (the one listing each chat's tags) contains some list of tags related to the current user. PFQuery has a method called whereKey:containsAllObjectsInArray: which does exactly that.
To make it work, you need to be clear about whether the list of tags is an array of pointers to tag objects, or an array of strings that are tag names. Naturally, if tags on chats are stored as pointers to objects, then the second parameter should be an array of PFObject, and if they are strings, then the array parameter must be an array of NSString.
Unrelated to the semantics of the query, but important: Doing an unguarded, asynch query for anything in cellForRowAtIndexPath: will be unproductive. This method is called every time a cell scrolls into view, which happens arbitrarily often, and arbitrarily rapidly. Use another method to fetch the table's datasource, then reload the table once the data arrives.
(I think the post has been given a close vote because it asks a specific question, then presents the reader with a lot of code, much of it unrelated, leaving the reader to find the relevant query, and showing no indication of what's been tried so far. The site will work better for you if you give maximum help to those who might answer an otherwise good question).