Firebase Loop through Nested Data and Store in Array

Question

I'm trying to save a list of image url's to an empty array of strings to then show in a collection view. I'm having trouble looping through the dictionary to store the URLs.

I get the Firebase data in the EncounterTableViewController.swift , then have another detailed view controller EncounterDetailViewController.swift that has an EncounterCollectionViewCell.swift

Encounter.swift

class Encounter {
    ...
    ...
    var images: [String] = []
}

EncounterTableViewController.swift

func showAllEncounters() {
    // Firebase tableview data
    FIRDatabase.database().reference().child("encounters").observeSingleEvent(of: .value, with: { (snapshot) in
        for rest in snapshot.children.allObjects as! [FIRDataSnapshot] {
            guard let restDict = rest.value as? [String: Any] else { continue }

            let encounter = Encounter()
            ...
            ...
            let mediaDict = restDict["media"] as! [[String:Any]]

            // need to find nested images and set them to encounter.images here

            self.encounters.append(encounter)

            self.tableView.reloadData()
        }
    })
}

EncounterDetailViewController.swift

private let reuseIdentifier = "imageCell"

class EncounterDetailViewController: UIViewController, 
UICollectionViewDataSource, UICollectionViewDelegate {

// MARK: - Properties
var selectedEncounter: Encounter?

// MARK: - View did load
override func viewDidLoad() {
    super.viewDidLoad()

}

    // MARK: - UICollectionViewDataSource
func numberOfSections(in collectionView: UICollectionView) -> Int {
    return 1
}

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return (selectedEncounter?.images.count)!
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as! EncounterCollectionViewCell

    cell.imageView.sd_setImage(with: URL(string: (selectedEncounter?.images[indexPath.row])!))

    return cell
}

Encounter Data structure

encounters
  -12
    -name: "shark"
    -length: "3"
    -media
      -0
        -id: "3242"
        -url: "http://google.com"
        -thumb-url: "http://thisurl.com"
      -1
        -id: "4252"
        -url: "http://google.com"
        -thumb-url: "http://thisurl.com"

Nirav D · Accepted Answer · 2017-05-29 09:18:30Z

2

Instead of for loop, simplest solution is to use flatMap.

let mediaDict = restDict["media"] as! [[String:Any]]
images = mediaDict.flatMap { $0["thumb_url"] as? String }

This single line solution will reduce your code of for loop but if still want to go with loop then you can make it like this.

for media in mediaDict {
    if let url = media["thumb_url"] as? String {
        images.append(url)
    } 
}

answered May 29, 2017 at 9:18

Nirav D

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5 Comments

pjmanning Over a year ago

Thanks again @Nirav ;) - haven't used flatMap before but works wondrously

Nirav D Over a year ago

@VladPulichev Its array not dictionary compare your and my one, You are mentioning it dictionary Firebase making it array

Nirav D Over a year ago

@VladPulichev Media is array restDict["media"] as! [[String:Any]] and you are saying it that it is dictionary restDict["media"] as! [String:Any] Hope this gave you idea, When key is number firebase made it array in this case it is array not dictionary, thats why you are wrong This line restDict["Media"] as! Dictionary will give crash to op

Nirav D Over a year ago

@VladPulichev No it still not works because you are telling that it is dictionary but its not dictionary its Array of dictionary

Nirav D Over a year ago

@VladPulichev Glad you made it mate :)

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