ios - cellForItemAtIndexPath indexPath not called for multiple collection views in a single UIViewController -

i trying have multiple collection views in single view controller. have tried achieve using separate tags each collection views, seems me celforitematindexpath not being invoked. following code uiviewcontroller.

import uikit class homeviewcontroller: uiviewcontroller {   // mark: - iboutlets    @iboutlet weak var backgroundimageview: uiimageview!   @iboutlet weak var collectionview: uicollectionview!   @iboutlet weak var friendscollectionview: uicollectionview!    // mark: - uicollectionviewdatasource   private var interests = interest.createinterests()   private var friends = friends.createfriends()    override func preferredstatusbarstyle() -> uistatusbarstyle {     return .lightcontent   }    override func viewdidload() {     super.viewdidload()     self.collectionview.tag = 100;     self.friendscollectionview.tag = 200;     collectionview.registerclass(nsclassfromstring("interestcell"),forcellwithreuseidentifier:"cell");     friendscollectionview.registerclass(nsclassfromstring("friendcell"),forcellwithreuseidentifier:"cellb");      self.view.addsubview(collectionview)     self.view.addsubview(friendscollectionview)     print("view did load")   }    private struct storyboard {     static let cellidentifier = "interestcell"     static let friendidentifier = "friendcell"   } }   extension homeviewcontroller : uicollectionviewdatasource {   func numberofsectionsincollectionview(collectionview: uicollectionview) -> int {     print("number of sections 1")     return 1   }    func collectionview(collectionview: uicollectionview, cellforitematindexpath indexpath: nsindexpath) -> uicollectionviewcell {     print("trying this")     if collectionview.tag == 100 {       let cell = collectionview.dequeuereusablecellwithreuseidentifier(storyboard.cellidentifier, forindexpath: indexpath) as! interestcollectionviewcell        print("inside pluto")       return cell     }     else {       let cellb = friendscollectionview.dequeuereusablecellwithreuseidentifier(storyboard.friendidentifier, forindexpath: indexpath) as! friendlistcollectionviewcell       print("inside venus")       return cellb     }   }    func collectionview(collectionview: uicollectionview, numberofitemsinsection section: int) -> int {     print("hello")     if collectionview == collectionview {       print(interests.count)       return interests.count     }     else {       print("hmmm")       return friends.count      }   } } 

can please suggest i'm doing wrong?

to reach cellforitematindexpath method, have set collectionview datasource :

collectionview.datasource = self; friendscollectionview.datasource = self; 

also, better instead of using tags recognize each collection, using similar :

if (collectionview == self.collectionview) { } else if (collectionview == self.friendscollectionview) { // init friend cell ... }