How to call collectionView.reloadData() from reusable header button? - ios

Question

I have a button in my reusable header view that deletes information in the array that supplies the data for the collection view and header. I want it to also be able to perform collectionView.reloadData().
The issue is that I can't call collectionView.reloadData() from the header button because it doesn't recognize collectionView as a variable. If I call Builds().collectionView.reloadData() (Builds is the View controller) the app crashes because it says that it found nil while unwrapping optional. I know that simply calling collectionView.reloadData() isn't the problem because i have collectionView.reloadData() called in viewDidAppear() and that gives me no crashes.
Whats going on here? How can I get my collectionView to reload data after the button removes the data?
For reference:
Reusable Header:
import UIKit
class BuildsHeader: UICollectionReusableView {
#IBOutlet weak var headerLabel: UILabel!
#IBOutlet weak var deleteBuildButton: UIButton!
#IBAction func deleteBuildButton(sender: UIButton) {
for hero in heroes{ if hero.hero.name == heroForDetails.hero.name {
hero.builds.removeAtIndex(sender.tag)
heroForDetails = hero
}}
saveToDefaults(userProfile)
//Builds().collectionBuild.reloadData() runs just fine without this line
}
}
ViewController:
import UIKit
class Builds: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
#IBOutlet weak var collectionBuild: UICollectionView!
override func viewDidLoad() {
super.viewDidLoad()
collectionBuild.delegate = self
collectionBuild.dataSource = self
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func viewDidAppear(animated: Bool) {
collectionBuild.reloadData()
}
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
if let cell = collectionView.dequeueReusableCellWithReuseIdentifier("BuildCell", forIndexPath: indexPath) as? TalentsCell {
let build = heroForDetails.builds[indexPath.section]
switch (indexPath.row) {
case 0:
cell.configureCell(build["1"]! as! Talent)
case 1:
cell.configureCell(build["4"]! as! Talent)
case 2:
cell.configureCell(build["7"]! as! Talent)
case 3:
cell.configureCell(build["10"]! as! Talent)
case 4:
cell.configureCell(build["13"]! as! Talent)
case 5:
cell.configureCell(build["16"]! as! Talent)
case 6:
cell.configureCell(build["20"]! as! Talent)
default:
cell.configureCell(build["1"]! as! Talent)
}
return cell
}
return UICollectionViewCell()
}
func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
}
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 7
}
func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
return heroForDetails.builds.count
}
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
return CGSizeMake(50,50)
}
func collectionView(collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionReusableView {
let header = collectionView.dequeueReusableSupplementaryViewOfKind(UICollectionElementKindSectionHeader, withReuseIdentifier: "BuildsHeader", forIndexPath: indexPath) as! BuildsHeader
var buildDict = heroForDetails.builds[indexPath.section]
header.headerLabel.text = buildDict["name"] as! String
header.deleteBuildButton.tag = indexPath.section
return header
}
}

Answer 1

You can achieve that with delegation.
Create a protocol
Create a variable inside BuildsHeader for delegate
Call the delegate method in deleteBuildButton function
Now the code for BuildsHeader should look like this:
import UIKit
//**** The Protocol ****
protocol BuildsHeaderDelegate {
func updateCollectionView()
}
class BuildsHeader: UICollectionReusableView {
//**** Variable for the delegate ****
var delegate: BuildsHeaderDelegate?
#IBOutlet weak var headerLabel: UILabel!
#IBOutlet weak var deleteBuildButton: UIButton!
#IBAction func deleteBuildButton(sender: UIButton) {
for hero in heroes{ if hero.hero.name == heroForDetails.hero.name {
hero.builds.removeAtIndex(sender.tag)
heroForDetails = hero
}}
saveToDefaults(userProfile)
//**** Call the delegate method ****
self.delegate?.updateCollectionView()
}
}
In the viewForSupplementaryElementOfKind method of your collection view configure the delegate property of the header, like this:
let header = collectionView.dequeueReusableSupplementaryViewOfKind(UICollectionElementKindSectionHeader, withReuseIdentifier: "BuildsHeader", forIndexPath: indexPath) as! BuildsHeader
//**** Set this view controller to be the header's delegate ****
header.delegate = self
// rest of header setup
Make the Builds ViewController confirm to BuildsHeaderDelegate :
class Builds: UIViewController, BuildsHeaderDelegate, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
Implement BuildsHeaderDelegate's delegate method in the Builds view controller. you can put this right after your viewForSupplementaryElementOfKind method:
func updateCollectionView () {
//**** reload the collectionView ****
self.collectionBuild.reloadData()
}

Answer 2

Use Delegate to call the method:
protocol BuildsHeaderDelegate(){
func reloadCollectionView()
}
class BuildsHeader: UICollectionReusableView {
var delegate:BuildsHeaderDelegate!
#IBOutlet weak var headerLabel: UILabel!
#IBOutlet weak var deleteBuildButton: UIButton!
#IBAction func deleteBuildButton(sender: UIButton) {
for hero in heroes{ if hero.hero.name == heroForDetails.hero.name {
hero.builds.removeAtIndex(sender.tag)
heroForDetails = hero
}}
saveToDefaults(userProfile)
//##Call delegate method##
delegate.reloadCollectionView()
}
}
Conform delegate in View Controller and Assign it:
class Builds: UIViewController,delegate:BuildsHeaderDelegate , UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
#IBOutlet weak var collectionBuild: UICollectionView!
override func viewDidLoad() {
super.viewDidLoad()
collectionBuild.delegate = self
collectionBuild.dataSource = self
}
func reloadCollectionView() {
collectionBuild.reloadData()
}
func collectionView(collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionReusableView {
let header = collectionView.dequeueReusableSupplementaryViewOfKind(UICollectionElementKindSectionHeader, withReuseIdentifier: "BuildsHeader", forIndexPath: indexPath) as! BuildsHeader
//##Assign Delegate##
header.delegate = self
var buildDict = heroForDetails.builds[indexPath.section]
header.headerLabel.text = buildDict["name"] as! String
header.deleteBuildButton.tag = indexPath.section
return header
}
}