Swift & SwiftUI - Conditional global var

Question

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.

Steve M · Accepted Answer · 2022-01-26 15:59:06Z

1

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")  
        }
    }
}

answered Jan 26, 2022 at 15:59

Steve M

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