I am new in Swift and don't have much more idea on optional (! , ?). I tried to fetch data from plist, create Model and show to UITableView. Table data shows perfectly, but it shows with Optional() binding. I tried change ! to ? but unable to unwrap. Could you please, guide me to solve this problem.
Here is my code & output -
var fileName : String?
var dataArray : Array<SHQuesAns>?
For fetch data from pList -
func loadTableView(){
dataArray = SHDataAccess.init(fname: fileName).arrayFromPlist()
self.questionTableView.dataSource = self
self.questionTableView.delegate=self
self.questionTableView.reloadData()
}
SHDataAccess class -
import UIKit
var fileName : String!
class SHDataAccess: NSObject {
init(fname:String?) {
super.init()
fileName = fname
}
func arrayFromPlist() -> Array <SHQuesAns>?{
let dataPlists = NSMutableArray(contentsOfFile:NSBundle.mainBundle().pathForResource(fileName, ofType: "plist")!)
var dataObj : Array <SHQuesAns>? = Array()
for data in dataPlists! {
dataObj?.append(SHQuesAns.init(_dic: data as! NSDictionary))
}
return dataObj
}
}
And UITableView delegates -
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return dataArray == nil ? 0 : dataArray!.count
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let aCell = self.questionTableView.dequeueReusableCellWithIdentifier("qcell",forIndexPath: indexPath) as! SHQuestionCell
let q : SHQuesAns = dataArray![indexPath.row]
aCell.lblQuestion.text = "\(q.question)"
return aCell
}
Here is the output -
This will remove that Optional() text:
if let q = q.question as? String {
aCell.lblQuestion.text = "\(q.question!)"
} else {
aCell.lblQuestion.text = ""
}
The key is to unwrap the string contained in the question object so that when it is assigned to the text of the label, the Optional() part will not be included.
I’ve added support for the nil case if the question string is not defined.
You might also consider not making your dataObj array optional? what purpose does it serve to be optional? Seems to me that if you need to add items to the array then you know it should exist and since you've initialized it it will always exist but then may be empty. Instead just make it implicitly unwrapped and then return nil if there's no data, then the objects of the array won't all be optional.
if you have a default in mind that you would want the optional string to fall back to, a simple fix would be something like:
"\(q.question ?? "")"
which will default to an empty string if q.question is nil
also: be careful of all of your force unwraps. it might make more sense to have some guard statements or if let unwraps.
and swift array's can be written like so: var dataArray : [SHQuesAns]?
but there aren't many situations where you need to differentiate between a nil array and an empty array so you can just do var dataArray = [SHQuesAns]() and save yourself the need to unwrap
Related
I am facing the issue of "Cannot assign to immutable expression of type 'Bool'" . Please look at the below code. I am getting error in viewForHeaderInSection. Actually where should i do modification to make it work?.
struct VenueDetail {
var isVeg: Bool
}
struct VenueDetailDTOMapper {
static func map(_ dto: DetailDataDTO) -> VenueDetail {
return VenueDetail(isVeg: dto.isVeg)
}
}
In API Manager I have get the data from api and use above struct as follow
let venueDetail = VenueDetailDTOMapper.map(getDetail)
ViewModel:
enum VenueDetailVMTypes {
case veueInfoInfo
}
protocol VenueDetailVMItems {
var type: VenueDetailVMTypes { get }
}
struct VenueInfoViewModel: VenueDetailVMItems {
var type: VenueDetailVMTypes {
return .veueInfoInfo
}
var headerSection: VenueDetail
}
func cretaDataSource() {
if let getVenueDetails = self.venueDetails {
let vmType = VenueInfoViewModel(headerSection: getVenueDetails)
arrayDataSource.append(vmType)
}
}
func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
let headerView = UIView()
let venueDetailVMItems = viewModel.arrayDataSource[section]
switch venueDetailVMItems.type {
case .veueInfoInfo:
let headerCell = tableView.dequeueReusableCell(withIdentifier: kCellIdentifierVenueHeader) as! VenueHeaderTVCell
headerCell.updateCellData(detail: (venueDetailVMItems as! VenueInfoViewModel).headerSection)
headerCell.foodTypeHandler = { [weak self] (isOn) in
guard let strongSelf = self else {
return
}
strongSelf.viewModel.showOnlyVegMenu(shouldShowVeg: isOn)
(venueDetailVMItems as! VenueInfoViewModel).headerSection.isVeg = isOn. //Cannot assign to immutable expression of type 'Bool'
strongSelf.tableView.reloadData()
}
headerView.addSubview(headerCell)
break
}
return headerView
}
Structs are value types, so each time you assign a struct, it makes a copy. You're treating it as a reference type. Stripping away all the as! casting, what you've done is:
let value = array[index]
value.someBool = true
reloadData()
Even if value were mutable (which it could be), that wouldn't do anything. value is a copy of array[index], not a reference to it. If you want it to be a reference, then you need to make it a reference type (a class).
You've used a protocol and a "type" identifier, where what I think you really wanted was an enum with associated data:
enum VenueDetail {
case veueInfoInfo(VenueInfoViewModel)
}
With this, you get rid of all of the dangerous and complicated as! casting.
But all of that doesn't really change the issue you're describing. Either way (with a protocol or with an enum), what you need to do is:
var value = array[index]
// change value the ways you want; set the bool, etc.
array[index] = value
A structure is an aggregation of fields; if a particular structure instance is mutable, its fields will be mutable; if an instance is immutable, its fields will be immutable. A structure type must thus be prepared for the possibility that the fields of any particular instance may be mutable or immutable.
Please check this
So try to change let to be var
Make sure the the arrayDataSource is mutable user var not let
var arrayDataSource = [VenueInfoViewModel]()
After struggling i just create a method in viewModel that removes objects in array of type .venueInfo and reload, i know its kind of hack but time being i have no option. In case if somebody found better way, really appreciated
func changeHeaderSwitch(isVeg: Bool) {
arrayDataSource.removeAll { (venueDetailVMItems) -> Bool in
return venueDetailVMItems.type == .veueInfoInfo
}
if var getVenueDetails = self.venueDetails {
getVenueDetails.isVeg = isVeg
let vmType = VenueInfoViewModel(headerSection: getVenueDetails, arrayMenuInfo: [])
arrayDataSource.append(vmType)
}
}
I have the following dictionary that I am placing in an array.
//Collections
var myShotArray = [Any]()
var myShotDictionary = [String: Any]()
myShotDictionary = ["shotnumber": myShotsOnNet, "location": shot as Any, "timeOfShot": Date(), "period": "1st", "result": "shot"]
myShotArray.append(myShotDictionary as AnyObject)
I then pass the array over to my tableview
myGoalieInforamtionCell.fillTableView(with: [myShotArray])
In my TableView
var myShotArray = [Any]()
func fillTableView(with array: [Any]) {
myShotArray = array
tableView.reloadData()
print("myShotArray \(myShotArray)")
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = Bundle.main.loadNibNamed("ShotInformationTableViewCell", owner: self, options: nil)?.first as! ShotInformationTableViewCell
let positionInArray = myShotArray[indexPath.row] as! [String : Any] //Could not cast value of type 'Swift.Array<Any>' (0x103991ac0) to 'Swift.Dictionary<Swift.String, Any>' (0x1039929b0).
cell.myGoalieShotInformationShotNumberLabel.text = positionInArray["shotnumber"]! as? String
return cell
}
Why do I get the above error the subject?
Thanks in advance.
When you call myGoalieInforamtionCell.fillTableView you are passing [myShotArray] - those square brackets mean that you have put myShotArray inside another array, so what you are actually passing to fillTableView is [[[String:Any]]] - an array of array of dictionary.
You can fix your immediate problem by simply removing those brackets;
myGoalieInforamtionCell.fillTableView(with: myShotArray)
However, you have way too many Any's there. You should take advantage of Swift's strong typing, which will avoid this sort of error.
I would suggest that you use a Struct rather than a dictionary for your data and then you can type things correctly. Something like:
enum Period {
case first
case second
case third
case fourth
}
struct ShotInfo {
let shotNumber: Int
let location: String // Not sure what this type should be
let timeOfShot: Date
let period: Period
let result: Bool
}
var myShotArray = [ShotInfo]()
let shot = ShotInfo(shotNumber: myShotsOnNet, location: shot, timeOfShot: Date(), period: .first, result: true}
myShotArray.append(shot)
myGoalieInforamtionCell.fillTableView(with: myShotArray)
func fillTableView(with array: [ShotInfo]) {
myShotArray = array
tableView.reloadData()
print("myShotArray \(myShotArray)")
}
If you have this and you mistakenly said fillTableView(with: [myShotArray]) Xcode will tell you straight away that you have a mismatch between the argument type and the expected type which is much better than discovering your error at run time when your program crashes.
Here:
myGoalieInforamtionCell.fillTableView(with: [myShotArray])
You're wrapping your array in an additional array, so you are getting your array instead of your dictionary when you access it to populate your cell.
It should just be:
myGoalieInforamtionCell.fillTableView(with: myShotArray)
At a minimum you should be declaring myShotArray as [[String: Any]] and changing the parameter to fillTableView to also be [[String: Any]] so that the compiler would catch this mistake. It would also allow you to remove the force cast that is throwing your error.
You should really be creating a struct/class and passing an array of those instead of dictionaries though.
I'm playing around with custom cells.
With the great help from the stackoverflow community i've been able to put some code together. I'm able to fetch array values from a text string into a custom cell uilabel and uibutton, but the issue is - the fetched result is always the last object in the array.
Here is the code
func setUpQuestion()
{
// setting variables
var Question: String?
var option1: String?
// using a text string with custom separators
let text = ">>Here is the grocery question\n>>and another one\n--Apples\n-
-Oranges\n[pickApples]pickOranges\n[pickApples2]"
// splitting this string into four different arrays depending on the separator
let lines = split(text) { $0 == "\n" }
for line in lines {
if line.hasPrefix(">>") {
Question = line.substringFromIndex(advance(line.startIndex, 2))
} else if line.hasPrefix("[") {
if let index = line.rangeOfString("]")?.startIndex {
option1 = line.substringWithRange(Range<String.Index>(
start: advance(line.startIndex, 1), end: index))
}
}
}
// creating variables for appending the values - here I'm using a custom class called QuestionMark created in a separate .swift file
var question1 = QuestionMark(Question: Question!, option:option1!)
var question2 = QuestionMark(Question: Question!, option:option1!)
// appending the values into uilabel and uibutton in the custom cell
arrayOfQuestions.append(question1)
arrayOfQuestions.append(question2)
}
// regular tableView protocol functions
func tableView(tableView: UITableView, numberOfRowsInSection
section: Int) ->Int
{
return arrayOfQuestions.count
}
func updateCount(){
if let list = mainTableView.indexPathsForSelectedRows() as? [NSIndexPath] {
rowsCount.text = String(list.count)
}
}
func tableView(tableView: UITableView, cellForRowAtIndexPath
indexPath: NSIndexPath) -> UITableViewCell
{
let cell: CustomCellForTableViewTableViewCell = tableView.dequeueReusableCellWithIdentifier("Cell") as! CustomCellForTableViewTableViewCell
// the SetCell function i'm using here was created in a separate .swift file
let quest = arrayOfQuestions[indexPath.row]
cell.setCell(quest.Questme!, optionone: quest.optionize!)
cell.optionOne.backgroundColor = UIColor.redColor()
return cell
}
Here are the additional codes i'm using for the class and setCell function
class QuestionMark
{
var Questme: String?
var optionize: String?
init(Question: String, option: String)
{
self.Questme = Question
self.optionize = option
}
// separate swift file
func setCell(Question: String, optionone: String)
{
self.mainText.text = Question
self.optionOne.setTitle(optionone, forState:UIControlState.Normal)
}
As a result in both cells i'm getting the last object from the text string and it looks like this
And another one - PickApples2
And another one - PickApples2
How do i start appending cells from the first array value and then move forward to second,third,fourth ?
Any ideas are greatly appreciated.
Thank you.
First of all, the syntax of the text to parse is pretty complicated ;-) …
Second of all, the problem to get always the last object is that you create the array of questions after the repeat loop. At that moment the variables question and option contain always the last found string.
Here a solution:
After getting a question a new object QuestionMark is created and appended to the array (without the optionize property)
After getting an option the appropriate QuestionMark object is fetched from the array by an index counter, the property optionize is set and the counter is increased.
Two notes:
Variable names should always start with a lowercase letter. Even the syntax highlighter of StackOverflow follows that naming convention.
In my solution all variables are non-optionals.
class QuestionMark
{
var questme: String
var optionize: String
init(question: String, option: String = "")
{
self.questme = question
self.optionize = option
}
...
var arrayOfQuestions = [QuestionMark]()
func setupQuestion() {
let text = ">>Here is the grocery question\n>>and another one\n--Apples\n--Oranges\n[pickApples]pickOranges\n[pickApples2]"
// splitting this string into four different arrays depending on the separator
var counter = 0
var question = ""
var option = ""
let lines = split(text) { $0 == "\n" }
for line in lines {
if line.hasPrefix(">>") {
question = line.substringFromIndex(advance(line.startIndex, 2))
let questionMark = QuestionMark(question: question)
arrayOfQuestions.append(questionMark)
} else if line.hasPrefix("[") {
if let index = line.rangeOfString("]")?.startIndex {
option = line.substringWithRange(Range<String.Index>(
start: advance(line.startIndex, 1), end: index))
let questionMark = arrayOfQuestions[counter]
questionMark.optionize = option
counter++
}
}
}
}
I am loading some data into NSUserDefaults on application startup and when the user views the according View loading the data out into a TableView. I'm having an issue with the data types though and always seem to get an error whichever way I try.
Where am I going wrong. I am skipping some code and only giving the important parts. I keep getting errors like "Can't assign Bool to AnyObject"
// startup function which loads the data
var categorys : [[String:Bool]] = [["All": true]]
for (index: String, category: JSON) in output {
categorys.append([category["name"].string!: true])
}
NSUserDefaults.standardUserDefaults().setObject(categorys, forKey: "categorys")
// view controller
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
var categorys: [[String:Bool]] = []
func buildTableView() {
if let categorys = NSUserDefaults.standardUserDefaults().arrayForKey("categorys") {
for category in categorys {
self.categorys.append([category["name"] as! String: category["selected"] as! Bool])
}
// Was trying to just assign straight away but fails
// self.categorys = categorys
}
}
// then later on I want to be able to do the following
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
cell.textLabel?.text = self.categorys[indexPath.row]["name"] as? String
}
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
if (self.categorys[indexPath.row]["selected"] as? Bool == true) {
self.categorys[indexPath.row]["selected"] = "false"
}
}
}
I should probably also mention i was trying a different datatype before which is more logical for my usage but also had similar issues.
["name": [category["name"].string!, "selected": true]]
I should also mention this is data for my tableview and I want to update the boolean value for if the cell is selected to not.
You said in the comment that you've got an error about "finding nil", but it's not really the same as an error about "Can't assign Bool to AnyObject"...
For your nil error, you have to replace those forced typecasts:
category["name"] as! String
with optional binding:
if let name = category["name"] as? String {
}
Now it will fail but not crash if a property is nil, and will properly append to the array of dictionaries:
let category = ["name":"me", "selected":true]
var categorys: [[String:Bool]] = []
if let name = category["name"] as? String, let selected = category["selected"] as? Bool {
categorys.append([name:selected])
} else {
// oops, a value was nil, handle the error
}
Same for your other operations, don't use forced casts:
if let myBool = self.categorys[indexPath.row]["selected"] where myBool == true {
self.categorys[indexPath.row]["selected"] = false
}
And since self.categorys[indexPath.row]["selected"] is a Bool type, don't assign a string like "false" but the actual false value.
In order to use Bool in NSUserDefaults, you must use setBool: forKey: :
NSUserDefaults.standardUserDefaults().setBool(true, forKey: "key")
otherwise it's problematic and you have to do workarounds, like storing the Bool in NSNumber or String.
I'm loading a list of objects from a core data database into a table view.
class ScheduleViewController: UITableViewController {
private var items: [AnyObject]?
// MARK: - Table view data source
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if let itemCount = items?.count {
return itemCount
}
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("DayScheduleCell", forIndexPath: indexPath) as DayScheduleCell
if let act = items[indexPath.row] as Activity {
if act.client != nil {
// ...
}
}
return cell
}
}
The data is retrieved inside a closure so I have declared an items array as an optional because it might be nil in the first run.
I'm getting the error '[AnyObject]?' does not have a member named 'subscript' at this line if let act = items[indexPath.row] as? Activity.
I can't figure out how to resolve this.
The array is declared as:
private var items: [AnyObject]?
so, as you also said, it's an optional
In swift an optional is an enum, so a type on its own - and as an optional, it can contain either a nil value or an object of the contained type.
You want to apply the subscript to the array, not to the optional, so before using it you have to unwrap the array from the optional
items?[indexPath.row]
but that's not all - you also have to use the conditional downcast:
as? Activity
because the previous expression can evaluate to nil
So the correct way to write the if statement is
if let act = items?[indexPath.row] as? Activity {
First of all you need to unwrap or optional chain the items as it can be nil. AnyObject has different behaviour when getting as element from array, due to the fact that AnyObject can be a function. You would have to cast from items like this:
if let act = items?[indexPath.row] as AnyObject? as Activity? {
if act.client != nil {
// ...
}
}
If items will never contain a function you can use
private var items: [Any]?
instead and cast with:
if let act = items?[indexPath.row] as? Activity {
if act.client != nil {
// ...
}
}
I have fixed my problem by convert index var type from UInt to Int
let obj = items[Int(index)]
Hope this can help someone who still get this problem.