Easy Publishers

#swiftobservable

Ever wondered how to create a simple publisher?

In this blog i'll try to show you the basics

Firstly we need to import the required frameworks

// Used for the ObservableObject import Combine // The easiest for publishers import SwiftUI

Published object

We're going to create a class what subclasses ObservableObject and contains a @Published variable.
(for this example it is also using a timer to update the value)

class MyObject: ObservableObject { // This published variable will be updated several times. @Published var y: String // Set a default value to y, and start the timer init() { // Set the value of y to Loading... y = "Loading..." // Run this function after 5 seconds on the main thread. DispatchQueue.main.asyncAfter(deadline: .now() + 5) { self.upd() // Update } } func upd() { // Set the value of y to Published World y = "Published World" // Tell the system that this ObservableObject class is updated. self.objectWillChange } }

(SwiftUI) View

struct MyView: View { // Define our object(class) as Observed @ObservedObject var v = MyObject() var body: some View { Text(v.y) // This will change automatically if y is changed } }

Full code




import Combine 


import SwiftUI 


class MyObject: ObservableObject { 


@Published var y: String 


init() { 


y = "Loading..." 


DispatchQueue.main.asyncAfter(deadline: .now() + 5) { self.upd() }


}


func upd() {


 y = "Published World"


 self.objectWillChange 


} 


} 


struct MyView: View {


 @ObservedObject var v = MyObject()


 var body: some View { Text(v.y) } }