Is it possible to convert a string to a SwiftUI view? Something like JavaScript's eval(). In the code below I'm looking for an XXX function.
let uiString: String = “VStack { Text(\“hi there\”) }”
let view: some View = XXX(uiString)
!!! Not recommended !!! Do not try This at home!
Here is an example, but you need to consider any possible view, or may you just limit your work for just some special input, like I did.
PS: You can do some big optimization in codes to make it better and faster with using some more for loop, switch or enums, but at the end of the day, the things that I showed here is work of SwiftUI not us! And not recommended. It was just a show case that how code be done.
struct ContentView: View {
var body: some View {
StringDecoderView(string: "Circle().fill(Color.red); Rectangle()")
}
}
struct StringDecoderView: View {
let string: String
var body: some View {
let arrayOfComponents: [String] = string.components(separatedBy: ";")
var anyView: [CustomViewType] = [CustomViewType]()
for item in arrayOfComponents {
if item.contains("Circle()") {
if item.contains(".fill") && item.contains("Color.red") {
anyView.append(CustomViewType(anyView: AnyView(Circle().fill(Color.red))))
}
else {
anyView.append(CustomViewType(anyView: AnyView(Circle())))
}
}
else if item.contains("Rectangle()") {
anyView.append(CustomViewType(anyView: AnyView(Rectangle())))
}
}
return ForEach(anyView) { item in
item.anyView
}
.padding()
}
}
struct CustomViewType: Identifiable {
let id: UUID = UUID()
var anyView: AnyView
}
No, because Swift is compiled to machine code. There isn't an interpreter to evaluate arbitrary expressions on the go.
That sounds a lot like a security vulnerability. Why would you want to do that?
Related
I have this Store struct, which is a wrapper for all my data. It has a subscript operator which takes in a UUID, and returns the associated object.
This way, I can have a List bind to a selection variable, which has type UUID, and then in another view I can access the selected object from that UUID.
However, I'm experiencing an issue where my TextField which binds to the Store doesn't update. It does update if I wrap it in another Binding, or if I instead just use Text.
Here is an minimal reproducible example:
struct Person: Identifiable, Hashable {
let id = UUID()
var name: String
}
struct Store {
var data: [Person]
subscript(id: Person.ID) -> Person {
get {
data.first(where: { $0.id == id })!
}
set {
data[data.firstIndex(where: { $0.id == id })!] = newValue
}
}
}
struct ContentView: View {
#State var store = Store(data: [
Person(name: "Joe"),
Person(name: "Eva"),
Person(name: "Sam"),
Person(name: "Mary")
])
#State var selection: Person.ID?
var body: some View {
NavigationView {
List(store.data, selection: $selection) {
Text($0.name)
}
if let selection = selection {
// Creating a new Binding which simply wraps $store[selection].name
// fixes this issue. Or just using Text also works.
TextField("Placeholder", text: $store[selection].name)
}
else {
Text("No Selection")
}
}
}
}
To reproduce this issue, just click different names on the Sidebar. For some reason the detail view's TextField doesn't update!
This issue can also be resolved if we simply move the Store to a ObservableObject class with #Published.
Also, making the Store conform to Hashable doesn't help this issue.
I feel like I'm missing something very basic with SwiftUI. Is there any way to fix this?
EDIT:
I've changed out Store for an [Person], and I made an extension with the same subscript operator that is in Store. However, the problem still remains!
try this:
TextField("Placeholder", text: $store[selection].name)
.id(selection) // <-- here
I want to make a global variable in Swift, so that its Data is accessible to any view that needs it. Eventually it will be a var so that I can mutate it, but while trying to get past this hurdle I'm just using it as let
I can do that by putting this as the top of a file (seemingly any file, Swift is weird):
let myData: [MyStruct] = load("myDataFile.json)
load() returns a JSONDecoder(). MyStruct is a :Hashable, Codable, Identifiable struct
That data is then available to any view that wants it, which is great. However, I want to be able to specify the file that is loaded based on a condition - I'm open to suggestions, but I've been using an #AppStorage variable to determine things when inside a View.
What I'd like to do, but can't, is do something like:
#AppStorage("appStorageVar") var appStorageVar: String = "Condition1"
if(appStorageVar == "Condition2") {
let myData: [MyStruct] = load("myDataFile2.json")
}
else {
let myData: [MyStruct] = load("myDataFile.json")
}
I can do this inside a View's body, but then it's only accessible to that View and then I have to repeat it constantly, which can't possibly the correct way to do it.
You could change just change the global in an onChange on the AppStorage variable. This is an answer to your question, but you have the problem that no view is going to be updating itself when the global changes.
var myData: [MyStruct] = load("myDataFile.json)
struct ContentView: View {
#AppStorage("appStorageVar") var appStorageVar: String = "Condition1"
var body: some View {
Button("Change value") {
appStorageVar = "Condition2"
}
.onChange(of: appStorageVar) { newValue in
myData = load(newValue == "Condition1" ? "myDataFile.json" : "myDataFile2.json")
}
}
}
Sorry to make this post so long, but in hindsight I should have shown you the simpler instance of the issue so you could better understand what the problem is. I am assuming the same issue with ForEach is at the root cause of both of these bugs, but I could be wrong. The second instance is still included to give you context, but the first intance should be all you need to fully understand the issue.
First Instance:
Here is a video of the issue: https://imgur.com/a/EIg9TSm. As you can see, there are 4 Time Codes, 2 of which are favorite and 2 are not favorites (shown by the yellow star). Additionally, there is text at the top that represents the array of Time Codes being displayed just as a list of favorite (F) or not favorite (N). I click on the last Time Code (Changing to favorite) and press the toggle to unfavorite it. When I hit save, the array of Time Codes is updated, yet as you see, this is not represented in the List. However, you see that the Text of the reduced array immediately updates to FNFF, showing that it is properly updated as a favorite by the ObservedObject.
When I click back on the navigation and back to the page, the UI is properly updated and there are 3 yellow stars. This makes me assume that the problem is with ForEach, as the Text() shows the array is updated but the ForEach does not. Presumably, clicking out of the page reloads the ForEach, which is why it updates after exiting the page. EditCodeView() handles the saving of the TimeCodeVieModel in CoreData, and I am 99% certain that it works properly through my own testing and the fact that the ObservedObject updates as expected. I am pretty sure I am using the dynamic version of ForEach (since TimeCodeViewModel is Identifiable), so I don't know how to make the behavior update immediately after saving. Any help would be appreciated.
Here is the code for the view:
struct ListTimeCodeView: View {
#ObservedObject var timeCodeListVM: TimeCodeListViewModel
#State var presentEditTimeCode: Bool = false
#State var timeCodeEdit: TimeCodeViewModel?
init() {
self.timeCodeListVM = TimeCodeListViewModel()
}
var body: some View {
VStack {
HStack {
Text("TimeCodes Reduced by Favorite:")
Text("\(self.timeCodeListVM.timeCodes.reduce(into: "") {$0 += $1.isFavorite ? "F" : "N"})")
}
List {
ForEach(self.timeCodeListVM.timeCodes) { timeCode in
TimeCodeDetailsCell(fullName: timeCode.fullName, abbreviation: timeCode.abbreviation, color: timeCode.color, isFavorite: timeCode.isFavorite, presentEditTimeCode: $presentEditTimeCode)
.contentShape(Rectangle())
.onTapGesture {
timeCodeEdit = timeCode
}
.sheet(item: $timeCodeEdit, onDismiss: didDismiss) { detail in
EditCodeView(timeCodeEdit: detail)
}
}
}
}
}
}
Here is the code for the View Models (shouldn't be relevant to the problem, but included for understanding):
class TimeCodeListViewModel: ObservableObject {
#Published var timeCodes = [TimeCodeViewModel]()
init() {
fetchAllTimeCodes()
}
func fetchAllTimeCodes() {
self.timeCodes = CoreDataManager.shared.getAllTimeCodes().map(TimeCodeViewModel.init)
}
}
class TimeCodeViewModel: Identifiable {
var id: String = ""
var fullName = ""
var abbreviation = ""
var color = ""
var isFavorite = false
var tags = ""
init(timeCode: TimeCode) {
self.id = timeCode.id!.uuidString
self.fullName = timeCode.fullName!
self.abbreviation = timeCode.abbreviation!
self.color = timeCode.color!
self.isFavorite = timeCode.isFavorite
self.tags = timeCode.tags!
}
}
Second Instance:
EDIT: I realize it may be difficult to understand what the code is doing, so I have included a gif demoing the problem (unfortunately I am not high enough reputation for it to be shown automatically). As you can see, I select the cells I want to change, then press the button to assign that TimeCode to it. The array of TimeCodeCellViewModels changes in the background, but you don't actually see that change until I press the home button and then reopen the app, which triggers a refresh of ForEach. Gif of issue. There is also this video if the GIF is too fast: https://imgur.com/a/Y5xtLJ3
I am trying to display a grid view using a VStack of HStacks, and am running into an issue where the ForEach I am using to display the content is not refreshing when the array being passed in changes. I know the array itself is changing because if I reduce it to a string and display the contents with Text(), it properly updates as soon as a change is made. But, the ForEach loop only updates if I close and reopen the app, forcing the ForEach to reload. I know that there is a special version of ForEach that is specifically designed for dynamic content, but I am pretty sure I am using this version since I pass in '''id: .self'''. Here is the main code snippet:
var hoursTimeCode: [[TimeCodeCellViewModel]] = []
// initialize hoursTimeCode
VStack(spacing: 3) {
ForEach(self.hoursTimeCode, id: \.self) {row in
HStack(spacing: 3){
HourTimeCodeCell(date: row[0].date) // cell view for hour
.frame(minWidth: 50)
ForEach(row.indices, id: \.self) {cell in
// TimeCodeBlockCell displays minutes normally. If it is selected, and a button is pressed, it is assigned a TimeCode which it will then display
TimeCodeBlockCell(timeCodeCellVM: row[cell], selectedArray: $selectedTimeCodeCells)
.frame(maxWidth: .infinity)
.aspectRatio(1.0, contentMode: .fill)
}
}
}
}
I'm pretty sure it doesn't change anything, but I did have to define a custom hash function for the TimeCodeCellViewModel, which might change the behavior of the ForEach (the attributes being changed are included in the hash function). However, I have noticed the same ForEach behavior in another part of my project that uses a different view model, so I highly doubt this is the issue.
class TimeCodeCellViewModel:Identifiable, Hashable {
static func == (lhs: TimeCodeCellViewModel, rhs: TimeCodeCellViewModel) -> Bool {
if lhs.id == rhs.id {
return true
}
else {
return false
}
}
func hash(into hasher: inout Hasher) {
hasher.combine(id)
hasher.combine(isSet)
hasher.combine(timeCode)
hasher.combine(date)
}
var id: String = ""
var date = Date()
var isSet = false
var timeCode: TimeCode
var frame: CGRect = .zero
init(timeCodeCell: TimeCodeCell) {
self.id = timeCodeCell.id!.uuidString
self.date = timeCodeCell.date!
self.isSet = timeCodeCell.isSet
self.timeCode = timeCodeCell.toTimeCode!
}
}
Here is a snippet of what you need to make the code work.
See the comments for some basics of why
struct EditCodeView:View{
#EnvironmentObject var timeCodeListVM: TimeCodeListViewModel
//This will observe changes to the view model
#ObservedObject var timeCodeViewModel: TimeCodeViewModel
var body: some View{
EditTimeCodeView(timeCode: timeCodeViewModel.timeCode)
.onDisappear(perform: {
//*********TO SEE CHANGES WHEN YOU EDIT
//uncomment this line***********
//_ = timeCodeListVM.update(timeCodeVM: timeCodeViewModel)
})
}
}
struct EditTimeCodeView: View{
//This will observe changes to the core data entity
#ObservedObject var timeCode: TimeCode
var body: some View{
Form{
TextField("name", text: $timeCode.fullName.bound)
TextField("appreviation", text: $timeCode.abbreviation.bound)
Toggle("favorite", isOn: $timeCode.isFavorite)
}
}
}
class TimeCodeListViewModel: ObservableObject {
//Replacing this whole thing with a #FetchRequest would be way more efficient than these extra view models
//IF you dont want to use #FetchRequest the only other way to observe the persistent store for changes is with NSFetchedResultsController
//https://stackoverflow.com/questions/67526427/swift-fetchrequest-custom-sorting-function/67527134#67527134
//This array will not see changes to the variables of the ObservableObjects
#Published var timeCodeVMs = [TimeCodeViewModel]()
private var persistenceManager = TimeCodePersistenceManager()
init() {
fetchAllTimeCodes()
}
func fetchAllTimeCodes() {
//This method does not observe for new and or deleted timecodes. It is a one time thing
self.timeCodeVMs = persistenceManager.retrieveObjects(sortDescriptors: nil, predicate: nil).map({
//Pass the whole object there isnt a point to just passing the variables
//But the way you had it broke the connection
TimeCodeViewModel(timeCode: $0)
})
}
func addNew() -> TimeCodeViewModel{
let item = TimeCodeViewModel(timeCode: persistenceManager.addSample())
timeCodeVMs.append(item)
//will refresh view because there is a change in count
return item
}
///Call this to save changes
func update(timeCodeVM: TimeCodeViewModel) -> Bool{
let result = persistenceManager.updateObject(object: timeCodeVM.timeCode)
//You have to call this to see changes at the list level
objectWillChange.send()
return result
}
}
//DO you have special code that you aren't including? If not what is the point of this view model?
class TimeCodeViewModel: Identifiable, ObservableObject {
//Simplify this
//This is a CoreData object therefore an ObservableObject it needs an #ObservedObject in a View so changes can be seem
#Published var timeCode: TimeCode
init(timeCode: TimeCode) {
self.timeCode = timeCode
}
}
Your first ForEach probably cannot check if the identity of Array<TimeCodeCellViewModel> has changed.
Perhaps you want to use a separate struct which holds internally an array of TimeCodeCellViewModel and conforms to Identifiable, effectively implementing such protocol.
stuct TCCViewModels: Identifiable {
let models: Array<TimeCodeCellViewModel>
var id: Int {
models.hashValue
}
}
You might as well make this generic too, so it can be reused for different view models in your app:
struct ViewModelsContainer<V: Identifiable> where V.ID: Hashable {
let viewModels: Array<V>
let id: Int
init(viewModels: Array<V>) {
self.viewModels = viewModels
var hasher = Hasher()
hasher.combine(viewModels.count)
viewModels.forEach { hasher.combine($0.id) }
self.id = hasher.finalize
}
}
When my Text gets it's string from an array, it doesn't localise, but when I hard-code it in, it does:
Localizable.strings
"greeting1" = "Hello there";
"greeting2" = "Howdy";
(Localised into English)
My View
var localisedStrings = ["greeting1", "greeting2"]
struct Message: View {
var body: some View {
ForEach(localisedStrings, id: \.self) { string in
Text(string)
}
}
}
The text will just write the key, like
"greeting1", rather than "Hello there"
Is there a way to force the Text object to use a localised string? Or is it changing somehow because it's getting it's content from a ForEach loop?
My View (hard coded)
//var localisedStrings = ["greeting1", "greeting2"]
struct Message: View {
var body: some View {
//ForEach(localisedStrings, id: \.self) { string in
Text("greeting1")
//}
}
}
This works just fine, and results in the text displaying "Hello there".
It works when you hardcode the string in, because you are using this initialiser, which takes a LocalizedStringKey.
LocalizedStringKey is ExpressibleByStringLiteral, but the word string in Text(string) is not a "string literal", so it calls this initialiser instead, and is not localised. You can initialise an instance of LocalizedStringKey directly, in order to localise it:
Text(LocalizedStringKey(string))
It's because here you are using plain String Swift type
var localisedStrings = ["greeting1", "greeting2"]
and here you are using SwiftUI own LocalizedStringKey type
Text("greeting1")
To fix your issue map your string to LocalizedStringKey
struct Message: View {
var body: some View {
ForEach(localisedStrings, id: \.self) { string in
Text(LocalizedStringKey(string))
}
}
}
Text.init(_:tableName:bundle:comment:)
Please follow the linked documentation to learn more.
I have a SummaryView with a Report as #State.
A Report is a protocol which includes some changes a user might want to make:
protocol Report {
var changeGroups: [ChangeGroup] { get set }
}
There are several kinds of reports; individual reports are implemented as a struct:
struct RealEstateReport: Report {
static let name = "Real Estate Report"
var changeGroups = [ChangeGroup]()
}
A ChangeGroup is a struct with (among other stuff) a human-readable summary and a handful of proposed changes:
struct ChangeGroup: Identifiable {
var summary: String
var proposedChanges = [ProposedChange]()
}
A ProposedChange is a class that represents one discrete change the app proposes to the user, which is enabled by default:
class ProposedChange: ObservableObject, Identifiable {
#Published var enabled = true
let summary: String
(In a detail view, enabled is bound to a Toggle so a user can flip each proposed change on and off.)
So a Report has many ChangeGroups which themselves have many ProposedChanges.
I'm trying to include some high level details on the SummaryView:
struct SummaryView: View {
#State var report: Report
var body: some View {
Text("Summary")
.foregroundColor(…) // ???
}
I want foregroundColor to be red, yellow, or green:
Red if enabled is false for all ProposedChanges in this Report
Green if enabled is true for all ProposedChanges in this Report
Yellow if enabled is mixed for different ProposedChanges in this Report
I've read a bit about Combine, and I think I need to create a new Combine subscription for each ChangeGroup, and map that to a new Combine subscription for each ProposedChange's enabled property, flatten the values when one changes, and check if they're all the same.
I'm a little lost on the exact syntax I'd use. And also it seems like structs don't publish changes in the same way (I guess since the structs are value vs. reference types).
How can I set the foregroundColor of the Text view based on the above logic?
Your issue is immediately solved if ProposedChange is a struct and not a class. Unless its instances have their own life cycle, then they are just holders of value, so should be semantically a struct.
The reason your issue is solved is because mutating a property of a struct mutates the struct, so SwiftUI knows to recompute the view, whereas with a class you need to subscribe to changes.
Assuming ProposedChange is a struct:
struct ProposedChange {
var enabled = true
var summary: String
}
the following should work:
struct SummaryView: View {
#State var report: Report
var body: some View {
Text("Summary")
.foregroundColor(summaryColor)
}
var summaryColor: Color {
let count = report.changeGroups.flatMap { $0.proposedChanges }
.map { ($0.enabled ? 1 : 0, 1) }
.reduce((0, 0), { ($0.0 + $1.0, $0.1 + $1.1) })
if count.0 == count.1 { return Color.green }
else if count.0 == 0 { return Color.red }
else { return Color.yellow }
}
}
I ended up mapping all the enabled flags to their publisher, combining them all using the CombineLatest operator, and then recalculating when the value changes:
class ViewModel: ObservableObject {
enum BoolState {
case allTrue, allFalse, mixed
}
#Published var boolState: BoolState?
private var report: Report
init(report: Report) {
self.report = report
report
.changeGroups // [ChangeGroup]
.map { $0.proposedChanges } // [[ProposedChange]]
.flatMap { $0 } // [ProposedChange]
.map { $0.$enabled } // [AnyPublisher<Bool, Never>]
.combineLatest() // AnyPublisher<[Bool], Never>
.map { Set($0) } // AnyPublisher<Set<Bool>, Never>
.map { boolSet -> BoolState in
switch boolSet {
case [false]:
return .allFalse
case [true]:
return .allTrue
default:
return .mixed
}
} // AnyPublisher<BoolState, Never>
.assign(to: &$boolState)
}
}
Note: .combineLatest() is not part of Combine but it's just an extension I wrote that iterates each pair of publishers in the array and calls them iteratively, like first.combineLatest(second).combineLatest(third) etc. If you need something more robust than this, it looks like the CombineExt project has a CombineLatestMany extension with several options.
At this point my view just does a #ObservedObject var viewModel: ViewModel and then uses viewModel.boolState in the body. Whenever any of the enabled flags change for any reason, the view updates successfully!