error.swift

extension View {
    func showError(error: Binding<Error?>, buttonTitle: String = "OK") -> some View {
        alert(
            error.wrappedValue?.localizedDescription ?? "Unknown error",
            isPresented: .constant(error.wrappedValue != nil)
        ) {
            Button(buttonTitle) {
                error.wrappedValue = nil
            }
        }
    }
}

public struct CustomError: Error {
    let message: String
}

extension CustomError: LocalizedError {
    public var errorDescription: String? {
        NSLocalizedString(message, comment: "")
    }
}

View.swift

import SwiftUI

struct ContentView: View {
    @State private var error: Error?
  
    var body: some View {
      Text("Hi")
        .task {
          doSomething()
        }
        .showError(error $error)
    }
  
    func doSomething() {
      do {
        try something()
      } catch {
        self.error = error
      }
    }
}