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I’m new to swift UI and programming in general. I’ve learnt the basics so far and now I want to be able to setup a simple form in my app. I can design the form no problem. But I’m not sure what function to call CIA the button action or the code to get that information from the user to a database. Can someone help to explain how to set that up and which database to use to collect the user information?
I can't set the database up for you, as each database has its unique ways of doing so. However, I am giving you a basic structure that would help you link your SwiftUI view to the back-end(your database).
Setting up your form
import SwiftUI
struct ContentView: View {
#State var firstName = ""
#State var lastName = ""
#State var age = ""
var body: some View {
TextField("Enter First Name", text: $firstName)
TextField("Enter Last Name", text: $lastName)
TextField("Age", text: $age)
Button(action: {
addUser(firstName: firstName, lastName: lastName, age: Int(age) ?? 0)
}) {
Text("Save to database")
}
}
}
Saving result to back-end:
import CoreData
func addUser(firstName: String, lastName: String, age: Int) {
/*
code here would be using Core Data structure
do not copy paste, only used as reference
*/
let newUser = User(context: context)
newUser.firstName = firstName
newUser.lastName = lastName
newUser.age = age
do {
try context.save()
print("Successfully saved to Core Data.")
} catch {
print(error.localizedDescription)
}
}
Keep in mind that you would have to do your own research on how to save results using your own database. The code in addUser() would not work if you are using something other than Core Data. In your case, I would suggest you to try Firebase and perhaps, you could use Firebase Firestore as it seems like it suits your needs.
Related
I am trying to remove the placeholder from a textfield in SwiftUI when user taps on the textfield. So as suggested in stackoverflow i used the following code.
import Foundation
import SwiftUI
import ApplicationCore
struct StartUpScreen: View {
#State var password = ""
#State var passwordPlaceholder = "Enter Password"
var body: some View {
TextField(self.$passwordPlaceholder.wrappedValue, text: $password, onEditingChanged: { (changed) in
print("Password onEditingChanged - \(changed)")
switch changed {
case true:
self.$passwordPlaceholder.wrappedValue
= self.$password.wrappedValue
self.$password.wrappedValue = ""
case false:
break
}
})
}
}
But when i run it nothing happens. The placeholder remains as it is when the user taps on the TextField box. So i just changed this line
self.$password.wrappedValue = ""
to this
self.$password.wrappedValue = " "
and it worked. So the answer i found in stackoverflow was wrong although everyone voted up for it so i thought it should work for me as well. Moreover the weird thing is that although i enter a space to work i do not see any spaces in my TextField and everything works great.
...but i want to understand what is going on behind the scenes.
Is there any logic explanation behind all this? Any help appreciated.
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I am currently trying to create a custom view in SwiftUI that basically behaves like a SwiftUI List or Form. What I want is to achieve is something like the following:
CustomView {
Text("TBD")
Text("TBD")
Image(systemName: "heart")
}
The output of this custom view should then be a vertical list of the views that were passed in, plus some additional elements, like dividers. Something like what you would get from the following code:
VStack(alignment: .leading) {
Text("TBD")
Divider()
Text("TBD")
Divider()
Image(systemName: "heart")
}
The problem is that I have no idea how to create a generic view that would take any number of other views and then arrange them in such a way - Im not even sure if it is possible.
If there is anyone around that has experience with creating something like this, I would appreciate any hints or explanations.
Thanks!
Here is an example that works for 3 views:
struct CustomView: View {
let children: [AnyView]
init<C1: View, C2: View, C3: View>(#ViewBuilder content: () -> TupleView<(C1, C2, C3)>) {
self.children = [AnyView(content().value.0),
AnyView(content().value.1),
AnyView(content().value.2)]
}
var body: some View {
VStack(alignment: .leading) {
children[0]
Divider()
children[1]
Divider()
children[2]
}
}
}
I believe you need an init for each number of Views you want to support. Read more about this here:
https://forums.swift.org/t/swiftui-viewbuilder-result-is-a-tupleview-how-is-apple-using-it-and-able-to-avoid-turning-things-into-anyview/28181/14
I have the following SwiftUI View:
struct ProductView: View {
#ObservedObject var productViewModel: ProductViewModel
var body: some View {
VStack {
ZStack(alignment: .top) {
if(self.productViewModel.product != nil) {
URLImage(url: self.productViewModel.product!.imageurl, itemColor: self.productViewModel.selectedColor)
}
else {
Image("loading")
}
}
}
}
that observes a ProductViewModel
class ProductViewModel: ObservableObject {
#Published var selectedColor: UIColor = .white
#Published var product: Product?
private var cancellable: AnyCancellable!
init(productFuture: Future<Product, Never>) {
self.cancellable = productFuture.sink(receiveCompletion: { comp in
print(comp)
}, receiveValue: { product in
self.product = product
print(self.product) // this prints the expected product. The network call works just fine
})
}
The Product is a Swift struct that contains several string properties:
struct Product {
let id: String
let imageurl: String
let price: String
}
It is fetched from a remote API. The service that does the fetching returns a Combine future and passes it to the view model like so:
let productFuture = retrieveProduct(productID: "1")
let productVM = ProductViewModel(productFuture: productFuture)
let productView = ProductView(productViewModel: productViewModel)
func retrieveProduct(productID: String) -> Future<Product, Never>{
let future = Future<Product, Never> { promise in
// networking logic that fetches the remote product, once it finishes the success callback is invoked
promise(.success(product))
}
return future
}
For the sake of brevity, I've excluded the networking and error handling logic since it is irrelevant for the case at hand. To reproduce this as quickly as possible, just initialize a mock product with some dummy values and pass it to the success callback with a delay like this:
let mockproduct = Product(id: "1", imageurl: "https://exampleurl.com", price: "$10")
DispatchQueue.main.asyncAfter(deadline: .now() + 2.0, execute: {
promise(.success(mockproduct))
})
Once the product arrives over the network, it is assigned to the published product property.
The fetching works and the correct value is assigned to the published property. Obviously this happens after the view has been created since the network call takes some time. However, the View never updates even though the published object is changed.
When I pass the product directly through the View Model initializer rather than the future, it works as expected and the view displays the correct product.
Any suggestions on why the view does not react to changes in the state of the view model when it is updated asynchronously through the combine future?
EDIT: When I asked this question I had the ProductViewModel + ProductView nested inside another view. So basically the productview was only a part of a larger CategoryView. The CategoryViewmodel initialized both the ProductViewModel and the ProductView in a dedicated method:
func createProductView() -> AnyView {
let productVM = productViewModels[productIndex]
return AnyView(ProductView(productViewModel: productVM))
}
which was then called by the CategoryView on every update. I guess this got the Published variables in the nested ProductViewModel to not update correctly because the view hierarchy from CategoryView downwards got rebuilt on every update. Accordingly, the method createProductView got invoked on every new update, resulting in a completely new initialization of the ProductView + ProductViewModel.
Maybe someone with more experience with SwiftUI can comment on this.
Is it generally a bad idea to have nested observable objects in nested views or is there a way to make this work that is not an antipattern?
If not, how do you usually solve this problem when you have nested views that each have their own states?
I have been iterating on patterns like this to find what I think works best. Not sure what the problem is exactly. My intuition suggests that SwiftUI is having trouble making updates on the != nil part.
Here is the pattern that I have been using which has been working.
Define an enum for states in your networking logic
public enum NetworkingModelViewState {
case loading
case hasData
case noResults
case error
}
Add the enumeration as a variable on your "View Model"
class ProductViewModel: ObservableObject {
#Published public var state: NetworkingModelViewState = .loading
}
Update the state as you progress through your networking
self.cancellable = productFuture.sink(receiveCompletion: { comp in
print(comp)
}, receiveValue: { product in
self.product = product
self.state = NetworkingModelViewState.hasData
print(self.product) // this prints the expected product. The network call works just fine
})
Now make a decision in your SwiftUI based on the Enum value
if(self.productViewModel.state == NetworkingModelViewState.hasData) {
URLImage(url: self.productViewModel.product!.imageurl, itemColor: self.productViewModel.selectedColor)
}
else {
Image("loading")
}
Musings ~ It's hard to debug declarative frameworks. They are powerful and we should keep learning them but be aware of getting stuck. Moving too SwiftUI has forced me to really think about MVVM. My takeaway is that you really need to separate out every possible variable that controls your UI. You should not rely on checks outside of reading a variable. The Combine future pattern has a memory leak that Apple will fix next release. Also, you will be able to switch inside SwiftUI next release.
I have a SwiftUI view that has a Form that contains a DatePicker:
struct GettingUpTimeSettingView: View {
#State private var viewModel = GettingUpTimeSettingViewModel()
var body: some View {
VStack {
Form {
Spacer()
Text(viewModel.questionString)
.accessibility(identifier: "Question")
Spacer()
DatePicker("Alarm Time",
selection: $viewModel.gettingUpTime,
displayedComponents: .hourAndMinute)
.accessibility(identifier: "Time")
.animation(.easeInOut)
Spacer()
Text(viewModel.explanationString)
.accessibility(identifier: "Explanation")
}
}
}
}
And an XCTestCase class for UI Testing:
class SleepyGPIntroUITests: XCTestCase {
private var app: XCUIApplication!
override func setUp() {
continueAfterFailure = false
app = XCUIApplication()
app.launch()
greeting = app.staticTexts["Greeting"]
}
override func tearDown() {
app = nil
}
func test_InitialScreen_ChangesTo_GettingUpScreen_Automatically() {
//Given
let questionText = "What time do you want to get up?"
let explanationText = "This should be the same time every day, including at weekends and on days off. Our best chance of great sleep comes when we have a regular routine."
let timeText = "7:00am"
let question = app.staticTexts["Question"]
let explanation = app.staticTexts["Explanation"]
let time = app.staticTexts["Time"]
//When
_ = time.waitForExistence(timeout: 2)
//Then
XCTAssertFalse(greeting.exists)
XCTAssertEqual(question.label, questionText, "Should show question at top of view")
XCTAssertEqual(explanation.label, explanationText, "Should show explanation in view")
XCTAssertEqual(time.label, timeText, "Should show the correct default time")
}
When I run the test, it fails and gives me this message:
Failed to get matching snapshot: No matches found for Elements matching predicate '"Time" IN identifiers' from input {(
StaticText, identifier: 'Question', label: 'What time do you want to get up?',
StaticText, identifier: 'Explanation', label: 'This should be the same time every day, including at weekends and on days off. Our best chance of great sleep comes when we have a regular routine.'
)}
I'm not sure whether this is down to the DatePicker() being contained in a Form, or whether it's because I'm not using the correct XCUIElementQuery to find it?
When I move the DatePicker outside the Form, I can find it, but only by using its label, and not its accessibility identifier.
The accessibility identifiers are working fine for the Text objects.
I can also find it using
app.datePickers.firstMatch
when it's outside the form, but not when it's contained within it.
I've found this answer that describes some odd behaviour when SwiftUI objects are contained in forms, but still haven't managed to solve my problem.
Many thanks.
tl:dr Can't get XCUIElementQuery to return DatePicker element when UITesting if the DatePicker is contained in a SwiftUI Form.
I've found the answer, for anyone that's interested.
First of all, a piece of basic advice, if you're struggling to find out how to access an element when UI testing in XCode, just use the record function and access the element manually.
That's what I did, and it showed me that before a DatePicker() is tapped on in SwiftUI, it actually shows as a button, so to access it in the example above I used this code:
let alarmTimeButton = app.tables.buttons["Time"]
I'm looking at an example of using SwiftUI with Combine: MVVM with Combine Tutorial for iOS at raywenderlich.com. A ViewModel implementation is given like this:
class WeeklyWeatherViewModel: ObservableObject, Identifiable {
// 2
#Published var city: String = ""
// 3
#Published var dataSource: [DailyWeatherRowViewModel] = []
private let weatherFetcher: WeatherFetchable
// 4
private var disposables = Set<AnyCancellable>()
init(weatherFetcher: WeatherFetchable) {
self.weatherFetcher = weatherFetcher
}
}
So, this makes some sense to me. In a view observing the model, an instance of the ViewModel is declared as an ObservedObject like this:
#ObservedObject var viewModel: WeeklyWeatherViewModel
And then it's possible to make use of the #Published properties in the model in the body definition of the View like this:
TextField("e.g. Cupertino", text: $viewModel.city)
In WeeklyWeatherViewModel Combine is used to take the city text, make a request on it, and turn this in to [DailyWeatherRowViewModel]. Up to here, everything is rosey and makes sense.
Where I become confused is that quite a lot of code is then used to:
Trigger a fetch when city is changed.
Keep hold of the AnyCancellable that's looking up weather data.
Copy the output of the weather look up in to dataSource by a sink on the weather fetch Publisher`
It looks like this:
// More in WeeklyWeatherViewModel
init(
weatherFetcher: WeatherFetchable,
scheduler: DispatchQueue = DispatchQueue(label: "WeatherViewModel")
) {
self.weatherFetcher = weatherFetcher
_ = $city
.dropFirst(1)
.debounce(for: .seconds(0.5), scheduler: scheduler)
.sink(receiveValue: fetchWeather(forCity:))
}
func fetchWeather(forCity city: String) {
weatherFetcher.weeklyWeatherForecast(forCity: city)
.map { response in
response.list.map(DailyWeatherRowViewModel.init)
}
.map(Array.removeDuplicates)
.receive(on: DispatchQueue.main)
.sink(
receiveCompletion: { [weak self] value in
guard let self = self else { return }
switch value {
case .failure:
self.dataSource = []
case .finished:
break
}
},
receiveValue: { [weak self] forecast in
guard let self = self else { return }
self.dataSource = forecast
})
.store(in: &disposables)
}
If I look in Combine for the definition of the #Published propertyWrapper, it seems like all does is provide projectedValue which is a Publisher, which makes it seem like it ought to be possible for WeeklyWeatherViewModel to simply provide the Publisher fetching weather data and for the view to make use of this directly. I don't see why the copying in to a dataSource is necessary.
Basically, what I'm expecting is there to be a way for SwiftUI to directly make use of a Publisher, and for me to be able to put that publisher externally from a View implementation so that I can inject it. But I've no idea what it is.
If this doesn't seem to make any sense, that figures, as I'm confused. Please let me know and I'll see if I can refine my explanation. Thanks!
I don't have a definitive answer to this and I didn't find a magic way to have SwiftUI make use of a Publisher directly – it's entirely possible that there is one that eludes me!
I have found a reasonably compact and flexible approach to achieving the desired result, though. It cut down the use of sink to a single occurrence that attaches to the input (#Published city in the original code), which substantially simplifies the cancelation work.
Here's a fairly generic model that has an #Published input attribute and a #Published output attribute (for which setting is private). It takes a transform as input, and this is used to transform the input publisher, and is then sinked in to the output publisher. The Cancelable of the sink is stored.
final class ObservablePublisher<Input, Output>: ObservableObject, Identifiable {
init(
initialInput: Input,
initialOutput: Output,
publisherTransform: #escaping (AnyPublisher<Input, Never>) -> AnyPublisher<Output, Never>)
{
input = initialInput
output = initialOutput
sinkCancelable =
publisherTransform($input.eraseToAnyPublisher())
.receive(on: DispatchQueue.main)
.sink(receiveValue: { self.output = $0 })
}
#Published var input: Input
#Published private(set) var output: Output
private var sinkCancelable: AnyCancellable? = nil
}
If you wanted a substantially less generic kind of model, you can see it's pretty easy to set up having the input (which is a publisher) be filtered in to the output.
In a view, you might declare an instance of the model and use it like this:
struct SimpleView: View {
#ObservedObject var model: ObservablePublisher<String, String>
var body: some View {
List {
Section {
// Here's the input to the model taken froma text field.
TextField("Give me some input", text: $model.input)
}
Section {
// Here's the models output which the model is getting from a passed Publisher.
Text(model.output)
}
}
.listStyle(GroupedListStyle())
}
}
And here's some silly setup of the view and its model taken from a "SceneDelegate.swift". The model just delays whatever is typed in for a bit.
let model = ObservablePublisher(initialInput: "Moo moo", initialOutput: []) { textPublisher in
return textPublisher
.delay(for: 1, scheduler: DispatchQueue.global())
.eraseToAnyPublisher()
}
let rootView = NavigationView {
AlbumSearchView(model: model)
}
I made the model generic on the Input and Output. I don't know if this will actually be useful in practice, but it seems like it might be.
I'm really new to this, and there might be some terrible flaws in this such as inefficiencies, memory leaks or retain cycles, race conditions, etc. I've not found them yet, though.
You can use URLSessionDataTaskPublisher and refactor out networking from all view models.
If you feel some part of the tutorial seems redundant, that is because it is.
MVVM in such usage is redundant and does not do the job better.
I have a refactored version (networking refactored, all view models removed) of that tutorial if you are interested in details.