I just wanna get all the records from the transaction variable and save it to an array.i tried and all I am getting is this constant error. please help me, I just wanna all models(records) to be saved on an array.
Type '()' cannot conform to 'View'
#State private var transactions: [Transactions] = [Transactions]()
ForEach(transactions, id: \.self) { transaction in
timexxx[0] = transaction.timexx ?? "0"
Text(timexxx[0] ?? "0")
}
enter image description here
Like what #multiverse has suggested
ForEach loop expects some sort of View but you are giving it or attempting to give an "array" (it only wants View)
Here is an updated code where you give the ForEach what it wants and you append to your timexxx array
ForEach(Array(transactions.enumerated()), id: \.offset) { (offset, transaction) in
Text(transaction.timexx ?? "\(offset)")
.onAppear {
timexxx[offset] = transaction.timexx ?? "\(offset)"
}
}
Update
for your question
"how do I do this with a simple "For" loop ? let's say I wanna do this operation in a simple class."
This is how it's done.
I removed the view Text.
for (i, transaction) in transactions.enumerated() {
timexxx[i] = transaction.timexx ?? "0"
}
Ok , so this is an error i faced as well, when i was learning SwiftUI( i am still a beginner), so now we need to understand , what does this error actually means, in this case the ForEach loop expects some sort of View but you are giving it or attempting to give an "array" (it only wants View)....
If you want values to be transferred to an array just simply create a function and do it .....
say you have a class and inside of which you do
#Published var song = [Song]()
then what you do is inside a function like loadData()
objects is the array whose elements you want transferred and most likely those elements belong to a Struct like Song here(if not its even simpler just use what ever type it has like Int, String etc.), this way all your elements will get transferred to song from objects
func loadData() {
song = objects.map {
artist in
Song(album: artist.album, artistImage: artist.artistImage)
}
}
Here i add the simplest possible way to transfer from one array to other
var objects = [1,2,3,4,5]
var song = [Int]()
func loadData() {
song = objects.map { $0 }
}
loadData()
print(song)
//[1,2,3,4,5]
Related
This carries on my last question struggling with value assignment to optional class variable, for which David provided me a good hint to a similar problem.
After numerous iterations I now came up with a different approach, however, it still fails and I have no idea why (and basically what happens)
I have the class definitions
struct HighScores: Codable {
var Scores:Int
var highscoreRecord: [HighscoreRecord]
}
struct HighscoreRecord: Codable {
var Rank:Int
var Date:String?
var avDuration:Float?
var Score:Int?
var Tries:Int?
}
In the view controller I have declared a variable of type HighScores, which may read the data from a JSON file or which may be initialized when setting the first high score.
class GameplayViewController: UIViewController {
var jsonResult: HighScores?
...
if firstHighscore == 1 {
jsonResult?.Scores = 1
jsonResult?.highscoreRecord.append(HighscoreRecord(Rank: 1, Date: formatter.string(from: dateStart), avDuration: Float(lblSpeed.text ?? "0.0"), Score: Int(lblRatio.text ?? "0"), Tries: hits + misses))
...
print(jsonResult)
This compiles and also runs. However, if I monitor the jsonResult variable, it still shows nil after assigning the Scores and and highscoreRecord values.
What happens, why can I assign a value without an error and without actually assigning it?
And first and foremost, how do I get my values into jsonResult?
Cheers
So following on from the comments above if you changed the code to be something along the lines of this you create the instance of the struct and add the values.
var jsonResult: HighScores?
if firstHighscore == 1 {
jsonResult = HighScores(Scores: 1, highscoreRecord: [HighscoreRecord(Rank: 1, Date: "your date", avDuration: 0.0, Score: 0, Tries: 0)])
}
once created you can add more highscorerecords to the array as needed, using the append method.
I am new to Swift and try to get a feeling for it by trying new things. Now I got stuck with lists. I have two arrays, one is the product and the other the price for each product. I want to fill a list by using a ForEach loop. I use a HStack to have two columns.
To make it a bit more clear, here are the two arrays:
#state private var products = ["Coke", "Fanta", "Sprite", "Water]
private var prices = ["1,43$", "1,22$", "1,64$", "0,45$"]
Now this is a part of my ContentView.swift:
var body: some View {
List{
ForEach(products, id: \.self) { product in
HStack{
Text(product)
Spacer()
Text(price[products.firstIndex(of: product)])
}
}
}
So my plan here is, to fill each cell with the product name by looping through the product array. Then I want to display the corresponding price. For that I take my second Text and fill it with the price. To find the correct Index of the price array, I get the Index from my products array, since they are similar.
That was my solution, but now I am getting an Error for the products.firstIndex(of: product).
I am getting following Error:
Value of optional type 'Array.Index?' (aka 'Optional') must be unwrapped to a value of type 'Array.Index' (aka 'Int')
I am not really understanding what this Error is trying to tell me.
Can anybody help?
The correct code looks like this:
struct ContentView: View {
private var products = ["Coke", "Fanta", "Sprite", "Water"]
private var prices = ["1,43$", "1,22$", "1,64$", "0,45$"]
var body: some View {
List{
ForEach(products, id: \.self) { product in
HStack{
Text(product)
Spacer()
Text(self.prices[self.products.firstIndex(of: product)!])
}
}
}
}
}
The reason for your error is that the array could be empty at some point which leads to a crash if you try to read firstIndex in that moment.
Now you have two options:
Force-unwrap with an "!" as I did above if you are sure the array will never be cleared/ be empty.
Provide a default value with "?? value" if the value may be nil at some point.
I have some user comments stored in a database (parse-server) that I would like to would like to display on my viewController's viewDidLoad(). I can easily pull the comment objects as follows:
super.viewDidLoad()
func query(){
let commentsQuery = PFQuery(className: "Comments")
commentsQuery.whereKey("objectId", equalTo: detailDisclosureKey)
commentsQuery.findObjectsInBackground { (objectss, error) in
if let objects = objectss{
if objects.count == 1{
for object in objects{
self.unOrderedComments.append(object)
}
}
}
}
}
This query dumps all of the of the comments in the unOrederedComments array. Each comment is added to the database with a createdAt property automatically being added relating the exact time of its creation. This property is a string with (as an example) the form: "2017-08-13T19:31:47.776Z" (the Z at the end is at the end of every string... not exactly sure why its there but its constant). Now, each new comment is added in order to the top of database and thus any queried result should be in order regardless. However, I would like to make sure of this by reordering it if necessary. My general thought process is to use .sorted, but I cannot figure out how to apply this to my situation
func orderComments(unOrderComments: [PFObject]) -> [PFObject]{
let orderedEventComments = unOrderedEventComments.sorted(by: { (<#PFObject#>, <#PFObject#>) -> Bool in
//code
})
}
This is the generic set up but I cannot, despite looking up several examples online figure out what to put in the <#PFObject#>'s and in the //code. I want to order them based on the "createdAt" property but this is not achieved via dot notation and instead requires PFObject["createdAt"] and using this notation keeps leading to error. I feel as so though I may need to set up a custom predicate but I do not know how to do this.
I was in the same situation, what I did was to first create an array of structs with the data I downloaded where I turned the string createdAt into a Date, then used this function:
dataArrayOrdered = unOrderedArray.sorted(by: { $0.date.compare($1.date) == .orderedAscending})
(.date being the stored Date inside my array of strcuts)
Try this code, notice that I assumed you have a variable name called ["Comments"] inside your Parse database, so replace if necessary. Also, I realised that createdAt it's in Date format, so there was no need to change it from String to Date, chek if it works the same for you, if it doesn't refer to this: Swift convert string to date.
struct Comment {
var date = Date()
var comment = String()
}
var unOrderedComments: [Comment] = []
var orderedComments = [Comment]()
override func viewDidLoad() {
super.viewDidLoad()
query()
}
func query(){
let commentsQuery = PFQuery(className: "Comments")
commentsQuery.findObjectsInBackground { (objectss, error) in
if let objects = objectss{
if objects.count >= 1{
for object in objects{
let newElement = Comment(date: object.createdAt!, comment: object["Comments"] as! String)
self.unOrderedComments.append(newElement)
print(self.unOrderedComments)
}
}
self.orderedComments = self.unOrderedComments.sorted(by: { $0.date.compare($1.date) == .orderedAscending})
print(self.orderedComments)
}
}
}
I have a RestAPI that pulls JSON data from a webpage, and because I want to follow MVC programming standards, I want to fetch this data through a "Data List" class that instantiates the RestAPI Class.
I have a class called "Card", which provides the basic structure of a type of data object. I have a class called "CardList" whose initialization creates an Array of the "Card" Classes.
However, I'm having trouble appending Card Class data to my CardList Array.
Here is the code for CardList Class:
class CardList {
var cards: [Card]
static var sharedInstance = CardList()
//MARK - Initalize
private init(){
//Dummy Data
let helm = Card(name: "Helm of Testing", cost: 10, type: "Equipment", subType: "Head Armor", description: "Some say the Helmet of Testing helps keep it's wearers mind clear.")
//Add to Array
var c = [helm]
let items: NSMutableArray = []
//Get API Array
RestApiManager.sharedInstance.getElements { (json: JSON) in
let results = json["results"]
for (_, subJson) in results {
let card:AnyObject = subJson["card"].object
items.addObject(card)
}
for var i = 0; i < items.count; ++i{
let data:JSON = JSON(items[i])
let newCard = Card(name: data["title"].stringValue, cost: Int(data["cost"].string!)!, type: data["type_id"].stringValue, subType: data["subtype_id"].stringValue, description: data["description"].stringValue)
c.append(newCard)
}
}
cards = c.sort { $0.cost < $1.cost }
}
//END Class
}
So basically on initialization, this class creates a dummy Card, adds it to an array called "c". An array called "items" is created. There RestApiManager returns JSON data, for every type of data returned in the results, it gets added into the "items" array.
We then loop through the "items" array, reading it as JSON (I'm using the SwiftyJSON plugin/code snip) and creating a new "Card" Class for each item in the array. We then append the "Card" to the "c" Array.
Finally we take the Card Array "cards" and set it equal to the "c" Array sorted by it's value cost.
The Problem:
After running the code, the "cards" Array only returns the dummy card named "helm", and none of the data added to the "c" array.
Notes:
Yes, my Api is working, if I print the values in the "for var i = 0" loop, it is printing correct values. If I print the "c.count" in the same loop, I get two (The API is only returning 1 other data set, or "Card"). If I print the "c.count" outside of that loop, after the loop, it says there is only 1 item in the Array when there should be two (the dummy data and the data returned from the JSON call).
So, it's clearly something with my syntax. Or maybe I'm making things more complicated than they need to. I'm fairly new to Swift and slightly confused. I just need someone else to look at my code.
Thank you in advance.
RestApiManager.sharedInstance.getElements works asynchronously.
The block containing the data is executed after the init function exits.
Move the code to assign and sort the array into the block.
...
for var i = 0; i < items.count; ++i{
let data:JSON = JSON(items[i])
let newCard = Card(name: data["title"].stringValue, cost: Int(data["cost"].string!)!, type: data["type_id"].stringValue, subType: data["subtype_id"].stringValue, description: data["description"].stringValue)
c.append(newCard)
}
cards = c.sort { $0.cost < $1.cost }
}
}
I haven't found anything on that in Swift. Have found how to find unique values on an array, but not this. Sorry if it sounds quite basic...
But I have the following array
var selectedValues = [String]()
And the following value that comes from a Parse query
var objectToAppend = object.objectForKey("description")! as! String
this is how I'am doing it at the moment.
self.selectedHobbies.append(objectToAppend)
But because the query happens repeated times, it ends up appending repeated values. It works, but I just want to not waste memory and only keep unique values.
Any ideas on how to solve that in swift?
You can use a Set which guarantees unique values.
var selectedValues = Set<String>()
// ...
selectedValues.insert(newString) // will do nothing if value exists
Of course, the elements of a Set are not ordered.
If you want to keep the order, just continue with the Array but check before you insert.
if !selectedValues.contains("Bar") { selectedValues.append("Bar") }
I guess that your problem was resolved but I add my answer for next developers who's facing same problem :)
My solution is to write an extension of Array to add elements from an array with a distinct way:
here the code :
extension Array{
public mutating func appendDistinct<S>(contentsOf newElements: S, where condition:#escaping (Element, Element) -> Bool) where S : Sequence, Element == S.Element {
newElements.forEach { (item) in
if !(self.contains(where: { (selfItem) -> Bool in
return !condition(selfItem, item)
})) {
self.append(item)
}
}
}
}
example:
var accounts: [Account]
let arrayToAppend: [Account]
accounts.appendDistinct(contentsOf: arrayToAppend, where: { (account1, account2) -> Bool in
return account1.number != account2.number
})