StepsEntity is a core data entity
Receiving the following error when attempting to display a string value in a TextField: "Cannot convert value of type 'Published<[StepsEntity]>.Publisher' to expected argument type 'Binding'"
I know this is because StepsEntity in my core data model is #Published. #Published works great here as it allows all the data to be updated neatly. How can I display an #Published in a TextField?
Below is the piece where I am receiving the error:
List {
VStack(alignment: .center) {
if let recipeSteps = (vm.recipes[vm.getRecordsCount() - 1].steps?.allObjects as? [StepsEntity])?.sorted { $0.stepNumber < $1.stepNumber } {
if (textFieldCount == 1) {
//do nothing
} else if (textFieldCount > 1) {
ForEach(recipeSteps, id: \.stepNumber) { index in
HStack {
Text(String(index.stepNumber) + ".").bold()
TextField("", text: vm.$recipeSteps) //This is where the error is seen
}
}.onDelete(perform: { index in
self.vm.deleteRecipeSteps(at: index, from: vm.recipes[vm.getRecordsCount() - 1])
})
}
}
}
vm.recipeSteps refers to my CoreDataRelationshipViewModel, which is where all core data functions are handled. this is declared in the view struct as:
#StateObject var vm = CoreDataRelationshipViewModel()
Here is a snippet from the CoreDataRelationshipViewModel class:
class CoreDataRelationshipViewModel: ObservableObject {
let manager = CoreDataManager.instance
#Published var recipes: [RecipeEntity] = []
#Published var recipeSteps: [StepsEntity] = []
init() {
getRecipes()
}
func getRecipes() { ////more functions for retrieving, deleting, etc. in this section
I have tried converting the Published var to a binding but no luck:
TextField("", text: Binding(vm.$recipeSteps)!)
I have also tried referencing the recipeSteps declared in the if let statement within the list, but that does not work either.
I have been at it for a few days, and I think I have exhausted all options. Open to all ideas here. Maybe I need to rebuild my model?
Thoughts?
--Edits--
Upper portion of struct, where variables are created:
struct AddItemView: View {
#StateObject var viewModel = ViewModel()
#State var frameDimensions: CGFloat = 0
#State var imageButtonText: String = "Click To Add Image"
#State var imageToUpload: Data
#StateObject var vm = CoreDataRelationshipViewModel()
#Environment(\.presentationMode) var presentationMode
#State var stepInfo: String = ""
#State var textFieldCount: Int = 1
#State var stepNumber: [Int]
#State var recordsCount = 1
#State var errorText = ""
#State var stepErrorColor = Color.white.opacity(0)
#State var nameErrorColor = Color.white.opacity(0)
var body: some View {
ZStack {
HStack {
Your problem is that
TextField("", text: vm.$recipeSteps)
should actually be
TextField("", text: $vm.recipeSteps)
as you need to pass the view model with Binding rather than recipeSteps (which, when using $ to pass it beyond vm's dot accessor, passes a generic Publisher).
Also, this would only work if the #Published property in your view model conforms to StringProtocol (is a string). Are you sure recipeSteps is a string that can be edited via TextField?
I ended up restructuring the way my core data save works. Instead of saving item by item, I am now looping through a for in loop to save data all at the end. This allows me to display the data locally via some state variables, but then save the full array to my core data entity.
Related
I'm brand new in Swift development, and I can't for the life of me figure this out. All I want to do is use an object to collect a forms data, save it to Realm, and then send it to the server via API.
In every example I've found, people are creating a new State variable for each element in their form. This seems unpractical for forms with many fields, so I tried to just create an object with properties that match the form fields I need. If I don't try to set any default values, this works as I expect. But when I try to set some default values for the form in the init(), I get errors that I don't know how to resolve. Here's some partial code:
The object that will be used to collect the form data:
class RecordObject: ObservableObject {
var routeId: Int?
var typeId: Int?
var inDate: Date?
var outDate: Date?
var nextDate: Date?
// .... more properties
}
And what I want to do is in the View, set some default values in the init() that need some logic to derive the value:
In the View:
struct AddLauncherView: View {
var route: Route // this is passed from a previous view that lists all the routes
#StateObject var record: RecordObject = RecordObject() // this is where I want to store all the form data
init(){
_record.routeId = self.route.id // I get the error: Referencing property 'routeId' requires wrapped value of type 'RecordObject'
self.record.inDate = Date() // this gives the error: 'self' used before all stored properties are initialized
//self.record.nextDate = here I need to do some date math to figure out the next date
}
var body: some View {
Form{
DatePicker("In Date", selection: $record.inDate, displayedComponents: .date)
// .... more form elements
}
}
}
I know I could add default values in the RecordObject class, but there are some properties that will need some logic to assign the default value.
Can someone help out a Swift noob and give me some pointers for making this work? Do I really need to create a State var for each form field in the View?
If you did use a class (ObservableObject), you'd want the properties to be annotated with #Published. However, it's probably a better idea to use a struct with a #State variable that contains all of the various properties you need. That may look like this:
struct Record {
var routeId: Int?
var typeId: Int?
var inDate: Date?
var outDate: Date?
var nextDate: Date?
}
struct AddLauncherView: View {
var route: Route
#State var record: Record
init(route: Route) {
self.route = route
_record = State(initialValue: Record(routeId: route.id,
typeId: nil,
inDate: Date(),
outDate: nil,
nextDate: nil))
}
var body: some View {
Form{
DatePicker("In Date",
selection: Binding<Date>(get: {record.inDate ?? Date()},
//custom binding only necessary if inDate is Date? -- if you make it just Date, you can bind directly to $record.inDate
set: {record.inDate = $0}),
displayedComponents: .date)
// .... more form elements
}
}
}
You are using the ObservableObject incorrectly. You data model should be a struct, and then the class publishes values that are of the type of the struct, so:
struct Record: Identifiable {
// First, save yourself some grief later and make it conform to Identifiable
let id = UUID()
// The listed variables are probably non-optional in your data model.
// If they are optional, mark them as optional, otherwise
var routeId: Int
var typeId: Int
var inDate: Date
// These are more likely optional
var outDate: Date?
var nextDate: Date?
// .... more properties
}
class RecordObject: ObservableObject {
// Make the source of truth #Published so things are updated in your view
#Published var records: [Record] = []
// OR use an init
#Published var records: [Record]
init(records: [Records] {
self.records = records
// or call some function that imports/creates the records...
}
}
noob here.
So Im coding a basic To-Do App and I need the user to be able to edit a task he previously entered. To do this, I wish to reuse my AddTaskView in the following way: once I tap "Edit" on the Task, the AddTaskView form gets presented and populated with all the Tasks data and pressing "Save" actually updates the data, instead of adding a new Task.
Currently, my AddTaskView stores all the forms variables in #State variables which have a value by default, such as:
#State private var taskTitle : String = ""
How can I send the data to AddTaskView that is already available since the task already exists to be able to populate the appropiate fields? My understanding is I cant just set #State variables values from outside the view.
Current AddTaskView.swift
struct AddTaskView: View {
//CoreDatas managedObjectEnvironment
#StateObject var vm : viewModel
#Environment(\.managedObjectContext) var moc
#Environment(\.presentationMode) var presentationMode
var categories : FetchedResults<Category>
#State private var taskTitle : String = ""
#State private var taskPriority : String = "Low"
#State private var chosenCategory : String? = ""
#State private var taskDate : Date = Date()
let priorities = ["Low", "High"]
var body: some View {
NavigationView {
Form {
Section(header: Text("Task info")) {
TextField("Task title", text: $taskTitle)
}
Section {
DatePicker("Date", selection: $taskDate)
}
Section {
Picker(
selection: $taskPriority,
label: Text("Priority")
) {
ForEach(self.priorities, id: \.self) {
Text($0).tag($0)
}
}
}
Section {
Picker(
selection: $chosenCategory,
label: Text("Category")
) {
ForEach(self.categories, id: \.categoryName) { cat in
Text(cat.categoryName ?? "Unknown").tag(cat.id)
}
}
}
Section {
Button("Save") {
self.vm.addTask(moc: self.moc, title: self.taskTitle, date: self.taskDate, priority: self.taskPriority, chosenCategory: chosenCategory!)
self.presentationMode.wrappedValue.dismiss()
}
}
}
.navigationTitle("Add Task")
}
}
I want to call and present this AddTaskView from another view where I have all the task info. As far as I understand, I cant just present the view such as:
AddTaskView(taskTitle: aTitle, taskPriority: aPriority, etc)
Any pointers are welcomed. thanks!
You did not ask a small question. I am going to recommend you go through Apple's Introducing SwiftUI. It will give you the foundation to understand what is going on, however the TLDR is every time you change an #State var in a struct, you are getting an entirely new struct. The values in a struct are immutable, regardless of what var might imply, and you literally make a new struct and put it in the old one's place.
And to answer your question as to presenting the view struct, yes, that would work. So would AddTaskView() the way you have your struct set up, though it wouldn't show much. Go hit the tutorial. It is well worth the time.
I have my parent view where I'm setting my States and I have two different views I'm trying to pass data between. When subview_1 calls subview_2 I'm not getting the binding data, the compiler fails with the error, The compiler is unable to type-check this expression in reasonable time; try breaking up the expression into distinct sub-expressions.
My parent view I've set the states
#State var businessPhone = ""
#State var businessRating = 0.0
In subview_1 I have my bindings set and the data works fine.
struct subview_1: View {
#Binding var businessRating: Double
#Binding var businessPhone: String
var body: some View {
....
}
}
When I call subview_2 from subview_1 the data isn't getting passed as expected.
struct subview_1: View {
#Binding var businessRating: Double
#Binding var businessPhone: String
var body: some View {
subview_2(businessRating: $businessRating, businessPhone: $businessPhone)
}
}
If I use .constant() with data that works as expected.
For subview_2 I have the following bindings set
#Binding var businessRating: Double
#Binding var businessPhone: String
I'm starting with SwiftUI and following WWDC videos I'm starting with #State and #Binding between two views. I got a display right, but don't get how to make back-forth read-write what was not include in WWDC videos.
I have model classes:
class Manufacturer {
let name: String
var models: [Model] = []
init(name: String, models: [Model]) {
self.name = name
self.models = models
}
}
class Model: Identifiable {
var name: String = ""
init(name: String) {
self.name = name
}
}
Then I have a drawing code to display that work as expected:
var body: some View {
VStack {
ForEach(manufacturer.models) { model in
Text(model.name).padding()
}
}.padding()
}
and I see this:
Canvas preview picture
But now I want to modify my code to allows editing this models displayed and save it to my model #Binding so I've change view to:
var body: some View {
VStack {
ForEach(self.$manufacturer.models) { item in
Text(item.name)
}
}.padding()
}
But getting and error in ForEach line:
Generic parameter 'ID' could not be inferred
What ID parameter? I'm clueless here... I thought Identifiable acting as identifier here.
My question is then:
I have one view (ContentView) that "holds" my datasource as #State variable. Then I'm passing this as #Binding to my ManufacturerView want to edit this in List with ForEach fill but cannot get for each binding working - how can I do that?
First, I'm assuming you have something like:
#ObservedObject var manufacturer: Manufacturer
otherwise you wouldn't have self.$manufacturer to begin with (which also requires Manufacturer to conform to ObservableObject).
self.$manufacturer.models is a type of Binding<[Model]>, and as such it's not a RandomAccessCollection, like self.manufacturer.models, which is one of the overloads that ForEach.init accepts.
And if you use ForEach(self.manufacturer.models) { item in ... }, then item isn't going to be a binding, which is what you'd need for, say, a TextField.
A way around that is to iterate over indices, and then bind to $manufacturer.models[index].name:
ForEach(manufacturer.indices) { index in
TextField("model name", self.$manufacturer.models[index].name)
}
In addition to that, I'd suggest you make Model (and possibly even Manufacturer) a value-type, since it appears to be just a storage of data:
struct Model: Identifiable {
var id: UUID = .init()
var name: String = ""
}
This isn't going to help with this problem, but it will eliminate possible issues with values not updating, since SwiftUI wouldn't detect a change.
I am working on a money input screen and I need to implement a custom init to set a state variable based on the initialized amount.
I thought the following would work:
struct AmountView : View {
#Binding var amount: Double
#State var includeDecimal = false
init(amount: Binding<Double>) {
self.amount = amount
self.includeDecimal = round(amount)-amount > 0
}
}
However, this gives me a compiler error as follows:
Cannot assign value of type 'Binding' to type 'Double'
How do I implement a custom init method which takes in a Binding struct?
Argh! You were so close. This is how you do it. You missed a dollar sign (beta 3) or underscore (beta 4), and either self in front of your amount property, or .value after the amount parameter. All these options work:
You'll see that I removed the #State in includeDecimal, check the explanation at the end.
This is using the property (put self in front of it):
struct AmountView : View {
#Binding var amount: Double
private var includeDecimal = false
init(amount: Binding<Double>) {
// self.$amount = amount // beta 3
self._amount = amount // beta 4
self.includeDecimal = round(self.amount)-self.amount > 0
}
}
or using .value after (but without self, because you are using the passed parameter, not the struct's property):
struct AmountView : View {
#Binding var amount: Double
private var includeDecimal = false
init(amount: Binding<Double>) {
// self.$amount = amount // beta 3
self._amount = amount // beta 4
self.includeDecimal = round(amount.value)-amount.value > 0
}
}
This is the same, but we use different names for the parameter (withAmount) and the property (amount), so you clearly see when you are using each.
struct AmountView : View {
#Binding var amount: Double
private var includeDecimal = false
init(withAmount: Binding<Double>) {
// self.$amount = withAmount // beta 3
self._amount = withAmount // beta 4
self.includeDecimal = round(self.amount)-self.amount > 0
}
}
struct AmountView : View {
#Binding var amount: Double
private var includeDecimal = false
init(withAmount: Binding<Double>) {
// self.$amount = withAmount // beta 3
self._amount = withAmount // beta 4
self.includeDecimal = round(withAmount.value)-withAmount.value > 0
}
}
Note that .value is not necessary with the property, thanks to the property wrapper (#Binding), which creates the accessors that makes the .value unnecessary. However, with the parameter, there is not such thing and you have to do it explicitly. If you would like to learn more about property wrappers, check the WWDC session 415 - Modern Swift API Design and jump to 23:12.
As you discovered, modifying the #State variable from the initilizer will throw the following error: Thread 1: Fatal error: Accessing State outside View.body. To avoid it, you should either remove the #State. Which makes sense because includeDecimal is not a source of truth. Its value is derived from amount. By removing #State, however, includeDecimal will not update if amount changes. To achieve that, the best option, is to define your includeDecimal as a computed property, so that its value is derived from the source of truth (amount). This way, whenever the amount changes, your includeDecimal does too. If your view depends on includeDecimal, it should update when it changes:
struct AmountView : View {
#Binding var amount: Double
private var includeDecimal: Bool {
return round(amount)-amount > 0
}
init(withAmount: Binding<Double>) {
self.$amount = withAmount
}
var body: some View { ... }
}
As indicated by rob mayoff, you can also use $$varName (beta 3), or _varName (beta4) to initialise a State variable:
// Beta 3:
$$includeDecimal = State(initialValue: (round(amount.value) - amount.value) != 0)
// Beta 4:
_includeDecimal = State(initialValue: (round(amount.value) - amount.value) != 0)
You should use underscore to access the synthesized storage for the property wrapper itself.
In your case:
init(amount: Binding<Double>) {
_amount = amount
includeDecimal = round(amount)-amount > 0
}
Here is the quote from Apple document:
The compiler synthesizes storage for the instance of the wrapper type by prefixing the name of the wrapped property with an underscore (_)—for example, the wrapper for someProperty is stored as _someProperty. The synthesized storage for the wrapper has an access control level of private.
Link: https://docs.swift.org/swift-book/ReferenceManual/Attributes.html -> propertyWrapper section
You said (in a comment) “I need to be able to change includeDecimal”. What does it mean to change includeDecimal? You apparently want to initialize it based on whether amount (at initialization time) is an integer. Okay. So what happens if includeDecimal is false and then later you change it to true? Are you going to somehow force amount to then be non-integer?
Anyway, you can't modify includeDecimal in init. But you can initialize it in init, like this:
struct ContentView : View {
#Binding var amount: Double
init(amount: Binding<Double>) {
$amount = amount
$$includeDecimal = State(initialValue: (round(amount.value) - amount.value) != 0)
}
#State private var includeDecimal: Bool
(Note that at some point the $$includeDecimal syntax will be changed to _includeDecimal.)
Since it's mid of 2020, let's recap:
As to #Binding amount
_amount is only recommended to be used during initialization. And never assign like this way self.$amount = xxx during initialization
amount.wrappedValue and amount.projectedValue are not frequently used, but you can see cases like
#Environment(\.presentationMode) var presentationMode
self.presentationMode.wrappedValue.dismiss()
A common use case of #binding is:
#Binding var showFavorited: Bool
Toggle(isOn: $showFavorited) {
Text("Change filter")
}
State:
To manages the storage of any property you declare as a state. When the state value changes, the view invalidates its appearance and recomputes the body and You should only access a state property from inside the view’s body, or from methods called.
Note: To pass a state property to another view in the view hierarchy, use the variable name with the $ prefix operator.
struct ContentView: View {
#State private var isSmile : Bool = false
var body: some View {
VStack{
Text(isSmile ? "😄" : "😭").font(.custom("Arial", size: 120))
Toggle(isOn: $isSmile, label: {
Text("State")
}).fixedSize()
}
}
}
Binding:
The parent view declares a property to hold the isSmile state, using the State property wrapper to indicate that this property is the value’s source of deferent view.
struct ContentView: View {
#State private var isSmile : Bool = false
var body: some View {
VStack{
Text(isSmile ? "😄" : "😭").font(.custom("Arial", size: 120))
SwitchView(isSmile: $isSmile)
}
}
}
Use a binding to create a two-way connection between a property that stores data, and a view that displays and changes the data.
struct SwitchView: View {
#Binding var isSmile : Bool
var body: some View {
VStack{
Toggle(isOn: $isSmile, label: {
Text("Binding")
}).fixedSize()
}
}
}
The accepted answer is one way but there is another way too
struct AmountView : View {
var amount: Binding<Double>
init(withAmount: Binding<Double>) {
self.amount = withAmount
}
var body: some View { ... }
}
You remove the #Binding and make it a var of type Binding
The tricky part is while updating this var. You need to update it's property called wrapped value. eg
amount.wrappedValue = 1.5 // or
amount.wrappedValue.toggle()
You can achieve this either with static function or with custom init.
import SwiftUI
import PlaygroundSupport
struct AmountView: View {
#Binding var amount: Double
#State var includeDecimal: Bool
var body: some View {
Text("The amount is \(amount). \n Decimals \(includeDecimal ? "included" : "excluded")")
}
}
extension AmountView {
static func create(amount: Binding<Double>) -> Self {
AmountView(amount: amount, includeDecimal: round(amount.wrappedValue) - amount.wrappedValue > 0)
}
init(amount: Binding<Double>) {
_amount = amount
includeDecimal = round(amount.wrappedValue) - amount.wrappedValue > 0
}
}
struct ContentView: View {
#State var amount1 = 5.2
#State var amount2 = 5.6
var body: some View {
AmountView.create(amount: $amount1)
AmountView(amount: $amount2)
}
}
PlaygroundPage.current.setLiveView(ContentView())
Actually you don't need custom init here at all since the logic could be easily moved to .onAppear unless you need to explicitly set initial state externally.
struct AmountView: View {
#Binding var amount: Double
#State private var includeDecimal = true
var body: some View {
Text("The amount is \(amount, specifier: includeDecimal ? "%.3f" : "%.0f")")
Toggle("Include decimal", isOn: $includeDecimal)
.onAppear {
includeDecimal = round(amount) - amount > 0
}
}
}
This way you keep your #State private and initialized internally as documentation suggests.
Don’t initialize a state property of a view at the point in the view
hierarchy where you instantiate the view, because this can conflict
with the storage management that SwiftUI provides. To avoid this,
always declare state as private, and place it in the highest view in
the view hierarchy that needs access to the value
.