Different ways to initialize a View Provider

[lookdeceline]

This post guides you through three main ways to initialize a View Provider.
The code snippets take GroupChannelViewProvider (or GroupChannelListViewProvider) for GroupChannelView (or GroupChannelListView) as an example, but it works the same for other View Providers as well.

version info: SendbirdSwiftUI 1.0.0+

Option 1. Declaring a View Provider as an @ObservedObject

• when to use this option: if the data necessary to create a View Provider is prepared in the parent view.

// Child View
struct MyView: View {
  @ObservedObject provider: GroupChannelListViewProvider
  
  var body: some View {
    GroupChannelListView(provider: provider) 
  }
}

// Parent View
struct ContentView: View {
  var body: some View {
    // Inject GroupChannelListViewProvider with necessary data from parent view.
    MyView(provider: createProvider())
  }

  private func createProvider() -> GroupChannelListViewProvider {
    let channelListQueryParams = GroupChannelListQueryParams { params in
        params.order = .latestLastMessage
        params.includeFrozenChannel = true
    }
    let channelListQuery = GroupChannel.createMyGroupChannelListQuery(params: params)
    return GroupChannelListViewProvider(channelListQuery: channelListQuery) 
  }
}

Option 2. Declaring a View Provider as a @StateObject and using the StateObject(wrappedValue:) init method

• when to use this option: if the data necessary to create a View Provider is ready at the time of your View's init method.

struct MyView: View {
  @StateObject var provider: GroupChannelListViewProvider
    
  init() {
    // Data necessary to create a View Provider is ready at the time of `init`.
    let params = GroupChannelListQueryParams()
    params.order = .channelNameAlphabetical
      
    // Initialize view provider.
    let channelListQuery = GroupChannel.createMyGroupChannelListQuery(params: params)
    _provider = StateObject(wrappedValue: GroupChannelListViewProvider(channelListQuery: channelListQuery))
  }
    
  var body: some View {
    GroupChannelListView(provider: provider)
  }
}

Option 3. Declaring a View Provider as a @StateObject and using the View Provider's .setup() method in .onAppear()

• when to use this option: if the data necessary to create a View Provider is fetched in an asynchronous fashion.
• All View Providers have .setup(...) method that lets you inject the necessary data into the View Provider after it had already been initialized.

struct MyView: View {
  @StateObject var provider = GroupChannelListViewProvider(channelURL: "")
    
  var body: some View {
    GroupChannelListView(provider: provider)
      .onAppear {
        provider.setup(channelURL: {CHANNEL_URL}
      }
  }
}