SOLVED: Got "Cannot find 'objectWillChange' in scope" error that I can't figure out why

@RoohBear

Jan '21

I'm following along with the instructions here https://www.hackingwithswift.com/books/ios-swiftui/manually-publishing-observableobject-changes

and I'm at the point where I'm supposed to invoke objectWillChange.send() when a variable changes. I understand that part, but I get this error and don't understand why

class FilterModel
{   
    @Published var value = 0 {
        willSet {
            objectWillChange.send()
            print("Hello from willSet")
        }
    }

If I remove the objectWillChange.send() line, I see "Hello from willSet" in my console log every 1.0 seconds.

@roosterboy HWS+

Jan '21

objectWillChange is a property of the ObservableObject protocol. You have to make FilterModel conform to that protocol in order to get rid of the message.

You also don't need both the @Published property wrapper and the willSet observer. @Published effectively already does behind the scenes what you are doing explicitly here. If you want to do further stuff when value is set, you would use the willSet with objectWillChange.send() but you would need to remove the @Published wrapper.

@RoohBear

Jan '21

Thank you! It turns out that some of the problems I was having was actually due to my data source being bad. I think things are working much better now that I'm making progress again :-)

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