Can I call MVVM cross command method from Ios based on condition?

Issue

I have below MVVM cross command in my viewmodel. I want to call this based on condition from iOS. Is this possible?

Command

public IMvxCommand LoginCommand
{
    get
    {
        return _loginCommand ?? (_loginCommand = new MvxCommand(async () => await ExecLoginClick()));
    }
}

iOS Binding

var bindings = this.CreateBindingSet<LoginView, LoginViewModel>();
bindings.Bind(username).To(vm => vm.Email);
bindings.Bind(password).To(vm => vm.Password);
bindings.Bind(login_button).To(vm => vm.LoginCommand);
bindings.Bind(forgot_button).To(vm => vm.ForgotCommand);
bindings.Bind(register_button).To(vm => vm.GetSignUpCommand);
//bindings.Bind(btn_facebook).To(vm=>vm.)
bindings.Apply();

Solution

You can use CanExecute for this.

public IMvxCommand LoginCommand
{
    get
    {
        return _loginCommand ?? 
        (_loginCommand = new MvxAsyncCommand(ExecLoginClick, CanLogin));
    }
}

private bool CanLogin()
{
    if ( /*your condition*/)
    {
        return true;
    }
    return false;
}

private Task ExecLoginClick()
{
    //...
}

And in every method, that affects your condition. You have to call

LoginCommand.RaiseCanExecuteChanged();

The Button is disabled or enabled based on the return value of CanExecute.

If you want to execute your command from your view, you should inherit from the generic MvxViewController<T> or MvxActivity<T> like.

public class LoginView : MvxViewController<LoginViewViewModel>
// or
public class LoginView : MvxActivity<LoginViewViewModel>

And then you can call

if(/*condition*/)
{
    ViewModel.LoginCommand.Execute();
}

Answered By - Sven-Michael Stübe