SwiftUI - Updating @State when Global changes

Question

I'd like to update an UI element on an overview view when data on another view is changed.

I looked into @EnvironmentalObject and @Binding. However, an update to either object does not appear to force a view reload. Only changes to @State force renders.
Also, in the case described below, the ChangeView is not a child of OverviewView. Therefore @Binding is not an option anyway.

Data.swift

struct ExampleData : Hashable { var id: UUID var name: String } var globalVar: ExampleData = ExampleData(id: UUID(), name:"")

OverviewView.swift

struct OverviewView: View { @State private var data: ExampleData = globalVar var body: some View { Text(data.name) } }

ChangeView.swift

struct ChangeView: View { @State private var data: ExampleData = globalVar var body: some View { TextField("Name", text: $data.name, onEditingChanged: { _ in globalVar = data }, onCommit: { globalVar = data }) } }

Changes within the ChangeView TextField will update the globalVar. However, this will not update the Text on the OverviewView when switching back to the view.

I am aware that using global variables is "ugly" coding. How do I handle data that will be used in a multitude of unrelated views?

Please advise on how to better handle such a situation.

Vlad · Accepted Answer · 2019-11-03 22:29:59Z

OverviewView and ChangeView hold different copies of the ExampleData struct in their data variables (When assigning a struct to another variable, you're effectively copying it instead of referencing it like an object.) so changing one won't affect the other.

@EnvironmentObject suits your requirements.

Here's an example:
Since, we're using @EnvironmentObject, you need to either convert ExampleData to a class, or use a class to store it. I'll use the latter.

class ExampleDataHolder: ObservableObject { @Published var data: ExampleData = ExampleData(id: UUID(), name:"") } struct CommonAncestorOfTheViews: View { var body: some View { CommonAncestorView() .environmentObject(ExampleDataHolder()) } } struct OverviewView: View { @EnvironmentObject var dataHolder: ExampleDataHolder var body: some View { Text(dataHolder.data.name) } } struct ChangeView: View { @EnvironmentObject var dataHolder: ExampleDataHolder var body: some View { TextField("Name", text: $dataHolder.data.name) } }

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