on Combine' @Published

[vinhnx]

tldr: @published is a wrapper for .objectWillChange, and with it, we don't need to call self.objectWillChange.send() manually on property's willSet/didSet

reference: https://twitter.com/luka_bernardi/status/1155944329363349504

In Beta 5 ObjectBinding is now defined in Combine as ObservableObject (the property wrapper is now @ObservedObject). There is also a new property wrapper @published where we automatically synthesize the objectWillChange publisher and call it on willSet.
It’ll objectWillChange.send() in the property willSet it’s defined on.
It just removes the boilerplate that you had to write before but otherwise behaves the same.

=> so @published in auto objectWillChange and call on willSet

reference: onmyway133/blog#487