Tony Merritt Tony Merritt - 3 years ago 77
iOS Question

Firebase Element May not exist on a call, iOS, Swift

I am using firebase database and storage to hold images and their descriptions. At the moment I have it coded to have 8 Images and 8 Descriptions. I am trying to work out how to get it so that if a user only selects4 pictures and puts in 4 descriptions that it allows that to be called back. It works fine with 8 but when I add 4 only and select that table to be called it crashes with an error that the 5th photo var doesn't hold anything.

below is the code I am using to call the data for the table and where it crashes.

func configureCell(post: Post) {
self.post = post
self.carImages = []

if post.imageUrl1 != "" {
self.carImages.append(post.imageUrl1)
}
if post.imageUrl2 != ""{
self.carImages.append(post.imageUrl2)
}
if post.imageUrl3 != "" {
self.carImages.append(post.imageUrl3)
}
if post.imageUrl4 != "" {
self.carImages.append(post.imageUrl4)
}
if post.imageUrl5 != "" {
print ("Tony: \(post.imageUrl5)")
self.carImages.append(post.imageUrl5)
}
if post.imageUrl6 != "" {
self.carImages.append(post.imageUrl6)
}
if post.imageUrl7 != "" {
self.carImages.append(post.imageUrl7)
}
if post.imageUrl8 != "" {
self.carImages.append(post.imageUrl8)
}


and the crash happens on imageUrl5

import Foundation
import Firebase

class Post {




private var _imageUrl1: String!
private var _imageUrl2: String!
private var _imageUrl3: String!
private var _imageUrl4: String!
private var _imageUrl5: String!
private var _imageUrl6: String!
private var _imageUrl7: String!
private var _imageUrl8: String!

private var _postKey: String!
private var _postRef: DatabaseReference!
private var _photoInfo1: String!
private var _photoInfo2: String!
private var _photoInfo3: String!
private var _photoInfo4: String!
private var _photoInfo5: String!
private var _photoInfo6: String!
private var _photoInfo7: String!
private var _photoInfo8: String!




var profileImageUrl: String {
return _profileImageUrl
}

var imageUrl1: String {
return _imageUrl1
}
var imageUrl2: String {
return _imageUrl2
}
var imageUrl3: String {
return _imageUrl3
}
var imageUrl4: String {
return _imageUrl4
}
var imageUrl5: String {
return _imageUrl5
}
var imageUrl6: String {
return _imageUrl6
}
var imageUrl7: String {
return _imageUrl7
}
var imageUrl8: String {
return _imageUrl8
}


var postKey: String {
return _postKey
}



var photoInfo1: String {
return _photoInfo1
}
var photoInfo2: String {
return _photoInfo2
}
var photoInfo3: String {
return _photoInfo3
}
var photoInfo4: String {
return _photoInfo4
}
var photoInfo5: String {
return _photoInfo5
}
var photoInfo6: String {
return _photoInfo6
}
var photoInfo7: String {
return _photoInfo7
}
var photoInfo8: String {
return _photoInfo8
}

init(imageUrl1: String, imageUrl2: String, imageUrl3: String, imageUrl4: String, imageUrl5: String, imageUrl6: String, imageUrl7: String, imageUrl8: String, photoInfo1: String, photoInfo2: String, photoInfo3: String, photoInfo4: String, photoInfo5: String, photoInfo6: String, photoInfo7: String, photoInfo8: String) {


self._imageUrl1 = imageUrl1
self._imageUrl2 = imageUrl2
self._imageUrl3 = imageUrl3
self._imageUrl4 = imageUrl4
self._imageUrl5 = imageUrl5
self._imageUrl6 = imageUrl6
self._imageUrl7 = imageUrl7
self._imageUrl8 = imageUrl8

self._photoInfo1 = photoInfo1
self._photoInfo2 = photoInfo2
self._photoInfo3 = photoInfo3
self._photoInfo4 = photoInfo4
self._photoInfo5 = photoInfo5
self._photoInfo6 = photoInfo6
self._photoInfo7 = photoInfo7
self._photoInfo8 = photoInfo8

}

init(postKey: String, postData: Dictionary<String, AnyObject>) {
self._postKey = postKey



if let imageUrl1 = postData["imageUrl1"] as? String {
self._imageUrl1 = imageUrl1
}
if let imageUrl2 = postData["imageUrl2"] as? String {
self._imageUrl2 = imageUrl2
}
if let imageUrl3 = postData["imageUrl3"] as? String {
self._imageUrl3 = imageUrl3
}
if let imageUrl4 = postData["imageUrl4"] as? String {
self._imageUrl4 = imageUrl4
}
if let imageUrl5 = postData["imageUrl5"] as? String {
self._imageUrl5 = imageUrl5
}
if let imageUrl6 = postData["imageUrl6"] as? String {
self._imageUrl6 = imageUrl6
}
if let imageUrl7 = postData["imageUrl7"] as? String {
self._imageUrl7 = imageUrl7
}
if let imageUrl8 = postData["imageUrl8"] as? String {
self._imageUrl8 = imageUrl8
}


if let photoInfo1 = postData["photoInfo1"] as? String {
self._photoInfo1 = photoInfo1
}
if let photoInfo2 = postData["photoInfo2"] as? String {
self._photoInfo2 = photoInfo2
}
if let photoInfo3 = postData["photoInfo3"] as? String {
self._photoInfo3 = photoInfo3
}
if let photoInfo4 = postData["photoInfo4"] as? String {
self._photoInfo4 = photoInfo4
}
if let photoInfo5 = postData["photoInfo5"] as? String {
self._photoInfo5 = photoInfo5
}
if let photoInfo6 = postData["photoInfo6"] as? String {
self._photoInfo6 = photoInfo6
}
if let photoInfo7 = postData["photoInfo7"] as? String {
self._photoInfo7 = photoInfo7
}
if let photoInfo8 = postData["photoInfo8"] as? String {
self._photoInfo8 = photoInfo8
}

_postRef = DataService.ds.REF_POSTS.child(_postKey)

}
}


Crash at 5th Image

Firebase Data

Jay Jay
Answer Source

Perhaps an answer via an example

We have a post class with a private var that's optional - meaning it could contain a value or could be nil. This is indicated with the String?

When the external imageUrl1 is accessed it may return a value or may be nil, again the ? indicates that.

class Post{
    private var _imageUrl1: String?

    var imageUrl1: String? {
        return _imageUrl1
    }

    init(url: String?) {  //this could be nil!
        self._imageUrl1 = url
    }
}

let aPost = Post(url: "testUrl")

if aPost.imageUrl1 != nil {
    print(aPost.imageUrl1!)
}

//or the preferred way which unwraps the optional automatically
if let aPostUrl = aPost.imageUrl1 {
    print(aPostUrl)
} else {
    print("it was nil")
}

//here's a nil example
let bPost = Post(url: nil)
if let bPostUrl = bPost.imageUrl1 {
    print(bPostUrl)
} else {
    print("it was nil")  //prints it was nil
}
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