What am I doing wrong here with my StateObject & @ObservedObject

Question

robevans OP

Created Oct ’21

Replies 1

Boosts 0

Participants 2

My view is called, but the default data is being used. My class is set like so

class UserWeatherData: ObservableObject {
  @Published var currentDescription = "It's gonna rain!"
}

My view:

struct WeatherView: View {

  @AppStorage("userTempChoice") var userTempChoice = "Fahrenheit"
  @ObservedObject var weather = UserWeatherData()
var body: some View {
    VStack {
    Text("Tap Me")
   .onTapGesture {
    I set my data
         }
       }
     }
   }

Here is where things are not working for me and weather.currentDescription is using the default data set above and not what I set.

struct SampleWeatherView: View {
  @StateObject var weather = UserWeatherData()

  var body: some View {
    Text(weather.currentDescription)
  }
}

Answered by OOPer in 691601022

To show the right usage of @StateObject, the relationship of two views needs to be clarified.

But generally, if there are two initializers in your code, there may be two or more different instances of the same class, which causes unexpected behavior.

Assuming your SampleWeatherView is a subview of WeatherView in your view hierarchy, you can write something like this:

WeatherView

struct WeatherView: View {
    
    @AppStorage("userTempChoice") var userTempChoice = "Fahrenheit"
    
    //Use only 1 `@StateObject` where the only initializer exists
    @StateObject var weather = UserWeatherData()
    
    var body: some View {
        VStack {
            SampleWeatherView(weather: weather)
            Text("Tap Me")
                .onTapGesture {
                    //I set my data
                    //A simplified working example
                    weather.currentDescription = "Sunny all day!!!"
                }
        }
    }
}

SampleWeatherView

struct SampleWeatherView: View {
    //Do not put an initializer except `@StateObject`
    @ObservedObject var weather: UserWeatherData
    
    var body: some View {
        Text(weather.currentDescription)
    }
}

If you could show more context representing the view hierarchy of your app, there might be the right solution other than above code.

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Answer 1

OOPer OP

Oct ’21

Accepted Answer