/// A type that publishes a property marked with an attribute.

///

/// Publishing a property with the `@Published` attribute creates a publisher of this type. You access the publisher with the `$` operator, as shown here:

///

///     class Weather {

///         @Published var temperature: Double

///         init(temperature: Double) {

///             self.temperature = temperature

///         }

///     }

///

///     let weather = Weather(temperature: 20)

///     cancellable = weather.$temperature

///         .sink() {

///             print ("Temperature now: \($0)")

///     }

///     weather.temperature = 25

///

///     // Prints:

///     // Temperature now: 20.0

///     // Temperature now: 25.0

///