environmentObject

EnvironmentObject is a property wrapper introduced in SwiftUI that allows for the observation and modification of external data sources within a SwiftUI view hierarchy. It is designed to share data that can be mutated by multiple views and have those changes automatically reflected across the application.

When you declare a property with the @EnvironmentObject, SwiftUI looks for an instance of that specific data type in the environment. The environment is a mechanism for passing data down the view hierarchy without explicitly passing it through initializers. If an instance is found, the view will be re-rendered whenever the observed object's published properties change. If no instance is found, it will lead to a runtime error, indicating that the object was not properly provided.

To make an EnvironmentObject available to a view and its descendants, you use the .environmentObject() modifier on a parent view. This modifier injects the provided object into the environment, making it accessible to any child view that declares a property with the @EnvironmentObject wrapper. This pattern is particularly useful for managing global application state, user preferences, or network services that need to be accessed from various parts of the UI. Unlike @State, which is local to a single view, or @ObservedObject, which is passed explicitly, @EnvironmentObject is designed for broader, implicit sharing of mutable state.