Create custom presenter for my mvvmcross project - mvvmcross

Question

I'm working on a project for iOS using mvvmcross.
App navigation goes like this: first it starts from the splash screen (1), them it navigates to (2), a view to select between 3 options, in view (3) and (4) you get a list and also could navigate back to (2), if you select an item in (3) you navigate to (5) in a modal way.
Lastly, all navigation end up in (6), a view with an hamburger menu.
So I have traditional navigation(with back button), modal views and a hamburger menu at the end.
It would be great if someone could help me or guide me to see how to create a custom presenter for this navigation scheme.
I'm using MvxModalNavSupportTouchViewPresenter and a SlidingPanelsNavigationViewController, but don't know how to swap them when I navigate from (2,4,5) to (6)

Answer 1

A presenter is just something that implements https://github.com/MvvmCross/MvvmCross/blob/develop/MvvmCross/Core/Core/Views/IMvxViewPresenter.cs
public interface IMvxViewPresenter
{
void Show(MvxViewModelRequest request);
void ChangePresentation(MvxPresentationHint hint);
}
This is are really simple interface and it allows shared portable code like ViewModels to request changes in the display.
For the case where you want a Show request to change the entire UI from one display paradigm (modal navigation controller) to another (sliding panels), then one way to do this is to implement a presenter which has two child presenters and which simply switches them over.
In pseudo code this might look like:
public class MyPresenter : IMvxViewPresenter
{
private IMvxViewPresenter _currentPresenter;
private ModalPresenter _modalPresenter;
private SlidingPresenter _slidingPresenter;
private enum Style
{
Modal, Panels
}
private Style _currentStyle;
public MyPresenter()
{
// do whatever you need to do here to:
// - construct _modalPresenter and _slidingPresenter
// - make _modalPresenter attached to the window (via root view controller)
// - make _slidingPresenter hidden/unattached
_currentStyle = Style.Modal;
_currentPresenter = _modalPresenter;
}
public void Show(MvxViewModelRequest request)
{
if (_currentStyle == Style.Modal &&
request.ViewModelType == typeof(WhateverViewModelIndicatesTheSwitchIsNeeded))
{
DoSwitch(request);
return;
}
_currentPresenter.Show(request);
}
public void ChangePresentation(MvxPresentationHint hint)
{
_currentPresenter.ChangePresentation(hint);
}
private void DoSwitch(MvxViewModelRequest request)
{
// do whatever is necessary to:
// - remove _modalPresenter from the window
// - add _panelPresenter to the window
// - show `request` within _panelPresenter
_currentPresenter = _panelPresenter;
_currentStyle = Style.Panelsl
}
}
Obviously, there are some details to fill in within this pseudo-code - e.g. there are some viewcontrollers to be added and removed from the window - but this is just standard iOS manipulation - e.g. see lots of questions and answers like Changing root view controller of a iOS Window and Change rootViewController from uiviewcontroller to uinavigationcontroller