Ambiguous reference to member 'collectionView(_:numberOfItemsInSection:)' when reloading collection view data

Question

In an app I've been writing, one of the tabs contains a Collection View that is originally filled with dummy information, but is supposed to be replaced once the user inputs some information in another tab. However, when I try to use self.collectionView?.reloadData() Xcode says Ambiguous reference to member 'collectionView(_:numberOfItemsInSection:)' . The code relevant to getting the data for the slots was removed. Does anyone here have any idea why it isn't working?

//
//  FirstViewController.swift
import UIKit
import Alamofire

class FirstViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {
    let reuseIdentifier = "cell" // also enter this string as the cell identifier in the storyboard
    var items = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "30", "31", "32", "33", "34", "35", "36", "37", "38", "39", "40", "41", "42", "43", "44", "45", "46", "47", "48"]


override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
    self.collectionView?.reloadData()

}

// MARK: - UICollectionViewDataSource protocol

// tell the collection view how many cells to make
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return self.items.count
}

// make a cell for each cell index path
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    // get a reference to our storyboard cell
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath as IndexPath) as! MyCollectionViewCell

    // Use the outlet in our custom class to get a reference to the UILabel in the cell
    cell.myLabel.text = self.items[indexPath.item]
    cell.backgroundColor = UIColor.white
    cell.layer.borderColor = UIColor.white.cgColor
    cell.layer.borderWidth = 5
    cell.layer.cornerRadius = 8// make cell more visible in our example project

    return cell
}

// MARK: - UICollectionViewDelegate protocol

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    // handle tap events
    print("You selected cell #\(indexPath.item)!")
}

}

Answer 1

You are using UIViewController and not UICollectionViewController so you don't get the collectionView property for free. You need to drag in an outlet form your storyboard and name it @IBOutlet var collectionView: UICollectionView!.