ios - UICollectionView cells do not take up width of UICollectionView -

the uicollectionview width change per device constrained reach horizontal margins of view. collectionview's layout flow. reason using uicollectionview space images evenly across on different device sizes, , of these images have tap gesture recogniser. , amount of rows variable, amount of image icons vary. apparently method after:

func collectionview(collectionview: uicollectionview, layout collectionviewlayout: uicollectionviewlayout, sizeforitematindexpath indexpath: nsindexpath) -> cgsize {     return cgsize(width: collectionviewwidth/6, height: collectionviewwidth/6); } 

i have tried this:

var collectionviewwidth: cgfloat = 0.0  override func viewdidload() {     super.viewdidload()      collectionview.datasource = self }  override func viewdidappear(animated: bool) {     collectionviewwidth = collectionview.collectionviewlayout         .collectionviewcontentsize().width }  func collectionview(collectionview: uicollectionview, layout collectionviewlayout: uicollectionviewlayout, sizeforitematindexpath indexpath: nsindexpath) -> cgsize {     return cgsize(width: collectionviewwidth/6, height: collectionviewwidth/6); } 

but nothing try in code makes difference @ final output (forget images not in uicollectionview - deleted):

i changed size of cells in interface builder , result got me this:

so have 2 questions:

why cells in above picture not go edge of uicollectionview?

how can set cell size programmatically @ run time make uicollectionview have 6 columns on device sizes?

here code viewcontroller contains uicollectionview:

import uikit  class dressingroomviewcontroller: uiviewcontroller {      @iboutlet weak var collectionview: uicollectionview!      let identifier = "cellidentifier"     let datasource = datasource()     var collectionviewwidth: cgfloat = 0.0      override func viewdidload() {         super.viewdidload()          collectionview.datasource = self     }      override func viewdidappear(animated: bool) {         collectionviewwidth = collectionview.collectionviewlayout             .collectionviewcontentsize().width     }      override func didreceivememorywarning() {         super.didreceivememorywarning()         // dispose of resources can recreated.     }      override func prepareforsegue(  segue: uistoryboardsegue,                                     sender: anyobject?) {         if (segue.identifier == "dressingroom2myoutfits") {             let myoutfitsviewcontroller = segue.destinationviewcontroller                 as! myoutfitsviewcontroller         }     } }    // mark:- uicollectionviewdatasource delegate extension dressingroomviewcontroller : uicollectionviewdatasource {      func numberofsectionsincollectionview(         collectionview: uicollectionview) -> int {             return datasource.groups.count     }      func collectionview(collectionview: uicollectionview,         numberofitemsinsection section: int) -> int {             return datasource.numbeofrowsineachgroup(section)     }      func collectionview(collectionview: uicollectionview,         cellforitematindexpath indexpath: nsindexpath) -> uicollectionviewcell {          let cell = collectionview.dequeuereusablecellwithreuseidentifier(             identifier,forindexpath:indexpath) as! fruitcell          let fruits: [fruit] = datasource.fruitsingroup(indexpath.section)         let fruit = fruits[indexpath.row]          let name = fruit.name!          cell.imageview.image = uiimage(named: name)         cell.caption.text = name.capitalizedstring          return cell     }      func collectionview(collectionview: uicollectionview, layout collectionviewlayout: uicollectionviewlayout, sizeforitematindexpath indexpath: nsindexpath) -> cgsize {         return cgsize(width: collectionviewwidth/6, height: collectionviewwidth/6);     } } 

it may worth mentioning data source of uicollectionview grouped because doing tutorial. here datasource code:

class datasource {

init() {     populatedata() }  var fruits:[fruit] = [] var groups:[string] = []  func numbeofrowsineachgroup(index: int) -> int {     return fruitsingroup(index).count }  func numberofgroups() -> int {     return groups.count }  func gettgrouplabelatindex(index: int) -> string {     return groups[index] }  // mark:- populate data plist  func populatedata() {     if let path = nsbundle.mainbundle().pathforresource(         "fruits", oftype: "plist") {             if let dictarray = nsarray(contentsoffile: path) {                 item in dictarray {                     if let dict = item as? nsdictionary {                         let name = dict["name"] as! string                         let group = dict["group"] as! string                          let fruit = fruit(name: name, group: group)                         if !contains(groups, group){                             groups.append(group)                         }                         fruits.append(fruit)                     }                 }             }     } }  // mark:- fruitsforeachgroup  func fruitsingroup(index: int) -> [fruit] {     let item = groups[index]     let filteredfruits = fruits.filter { (fruit: fruit) -> bool in         return fruit.group == item     }     return filteredfruits } 

}

and here plist gets loaded data source:

edit: have done work remove groups unneeded. see groups causing new rows start soon. changed code this:

    // mark:- uicollectionviewdatasource delegate extension dressingroomviewcontroller : uicollectionviewdatasource {      func numberofsectionsincollectionview(         collectionview: uicollectionview) -> int {             return 1     }      func collectionview(collectionview: uicollectionview,         numberofitemsinsection section: int) -> int {             return 12     }      func collectionview(collectionview: uicollectionview,         cellforitematindexpath indexpath: nsindexpath) -> uicollectionviewcell {          let cell = collectionview.dequeuereusablecellwithreuseidentifier(             identifier,forindexpath:indexpath) as! fruitcell          let fruits: [fruit] = datasource.fruits         let fruit = fruits[indexpath.row]          let name = fruit.name!          cell.imageview.image = uiimage(named: name)         cell.caption.text = name.capitalizedstring          return cell     }      func collectionview(collectionview: uicollectionview,         sizeforitematindexpath indexpath: nsindexpath) -> cgsize {             return cgsize(width: 200, height: 200);     } } 

now need make cell width 1/6 of collection view width somehow , crop off bottom of uicollectioview wasted space

you can set itemsize of collectionviewlayout in viewdidload shown in example:

    override func viewdidload() {         super.viewdidload()         let layout = collectionview.collectionviewlayout as! uicollectionviewflowlayout         let collectionviewsize = collectionview.frame.size         let nrofcellsperrow = 6          let itemwidth = collectionviewsize.width/nrofcellsperrow         let itemheight = 80 // example         layout.itemsize = cgsize(width: itemwidth, height: itemheight)      } 

if want have spacing between cells have compensate itemwidth calculation