Xamarin Forms iOS Validate Texbox and show error - mvvm

Question

I've customized the Xamarin Forms Entry control for Android,
I'm using MVVM Validation for validating my Inputs via MVVM and generate a message for each form element.
Validator.AddRequiredRule(() => UserName, Messages.FieldCannotBlank);
Validator.AddRequiredRule(() => Password, Messages.FieldCannotBlank);
The customised entry I've used is an extended version of the Extended Entry by Xlabs. Here's the code for the Entry
public class ExtendedEntry : Entry
{
public ExtendedEntry()
{
BorderColor = Color.Default;
BGColorForRounded = Color.Default;
}
#region XAlign
/// <summary>
/// The XAlign property
/// </summary>
public static readonly BindableProperty XAlignProperty =
BindableProperty.Create(nameof(XAlign), typeof(TextAlignment), typeof(ExtendedEntry),
TextAlignment.Start);
/// <summary>
/// Gets or sets the X alignment of the text
/// </summary>
public TextAlignment XAlign
{
get { return (TextAlignment)GetValue(XAlignProperty); }
set { SetValue(XAlignProperty, value); }
}
#endregion
#region BGColorForRounded
public static BindableProperty BGColorForRoundedProperty =
BindableProperty.Create(nameof(BGColorForRounded), typeof(Color), typeof(ExtendedEntry), default(Color));
public Color BGColorForRounded
{
get { return (Color)GetValue(BGColorForRoundedProperty); }
set { SetValue(BGColorForRoundedProperty, value); }
}
#endregion
#region Padding
public static BindableProperty PaddingProperty =
BindableProperty.Create(nameof(Padding), typeof(Thickness), typeof(ExtendedEntry), default(Thickness), defaultBindingMode: BindingMode.OneWay);
public Thickness Padding
{
get { return (Thickness)GetValue(PaddingProperty); }
set { SetValue(PaddingProperty, value); }
}
#endregion Padding
#region IsReadOnly
public static readonly BindableProperty IsReadOnlyProperty =
BindableProperty.Create("IsReadOnly", typeof(bool), typeof(ExtendedEntry), false);
public bool IsReadOnly
{
get { return (bool)GetValue(IsReadOnlyProperty); }
set { SetValue(IsReadOnlyProperty, value); }
}
#endregion
#region IsValid
public static readonly BindableProperty IsValidProperty =
BindableProperty.Create("IsValid", typeof(bool), typeof(ExtendedEntry), true);
public bool IsValid
{
get { return (bool)GetValue(IsValidProperty); }
set { SetValue(IsValidProperty, value); }
}
#endregion
#region ErrorHint
public static readonly BindableProperty ErrorHintProperty =
BindableProperty.Create("ErrorHint", typeof(string), typeof(ExtendedEntry), "");
public string ErrorHint
{
get { return (string)GetValue(ErrorHintProperty); }
set { SetValue(ErrorHintProperty, value); }
}
#endregion
#region PlaceholderTextColor
/// <summary>
/// The PlaceholderTextColor property
/// </summary>
public static readonly BindableProperty PlaceholderTextColorProperty =
BindableProperty.Create("PlaceholderTextColor", typeof(Color), typeof(ExtendedEntry), Color.Default);
/// <summary>
/// Sets color for placeholder text
/// </summary>
public Color PlaceholderTextColor
{
get { return (Color)GetValue(PlaceholderTextColorProperty); }
set { SetValue(PlaceholderTextColorProperty, value); }
}
#endregion
#region HasBorder
/// <summary>
/// The HasBorder property
/// </summary>
public static readonly BindableProperty HasBorderProperty =
BindableProperty.Create("HasBorder", typeof(bool), typeof(ExtendedEntry), true);
/// <summary>
/// Gets or sets if the border should be shown or not
/// </summary>
public bool HasBorder
{
get { return (bool)GetValue(HasBorderProperty); }
set { SetValue(HasBorderProperty, value); }
}
#endregion
#region BorderRadius
public int BorderRadius
{
get { return (int)GetValue(BorderRadiusProperty); }
set { SetValue(BorderRadiusProperty, value); }
}
// Using a DependencyProperty as the backing store for BorderRadius. This enables animation, styling, binding, etc...
public static readonly BindableProperty BorderRadiusProperty =
BindableProperty.Create("BorderRadius", typeof(int), typeof(ExtendedEntry), 0);
#endregion
#region BorderColor
/// <summary>
/// The Border Color Property
/// </summary>
public static readonly BindableProperty BorderColorProperty =
BindableProperty.Create("BorderColor", typeof(Color), typeof(ExtendedEntry), default(Color));
/// <summary>
/// Gets or sets the border color
/// </summary>
public Color BorderColor
{
get { return (Color)GetValue(BorderColorProperty); }
set { SetValue(BorderColorProperty, value); }
}
#endregion
}
Whenever a button is pressed, I call the Validators ValidateAll method to validate all my fields
var result = Validator.ValidateAll();
if (!result.IsValid)
{
App.Current.MainPage.DisplayAlert("Error", "The forms has errors, please review the errors and fix them.", "Ok");
}
Errors = result.AsDictionary();
Errors is another property of the Viewmodel which is basically a dictionary which will hold a list of key-value pairs of property names and errors after validation. I map this value to the ErrorHint property of my ExtendedEntry in Xaml
<controls:ExtendedEntry ErrorHint="{Binding Errors[UserName]}"
IsValid="{Binding Errors[UserName], Converter={StaticResource DictBool},
Mode=TwoWay}"
Placeholder="sallysmith#gmail.com"
Style="{DynamicResource WhiteEntryStandard}"
Text="{Binding UserName}" />
And to finish off, this is the implementation for Android
private void SetValidityAndHint(ExtendedEntry view)
{
if (!view.IsValid)
{
if (!string.IsNullOrEmpty(view.ErrorHint))
{
Control.Error = view.ErrorHint;
}
}
}
This works fine for Android. But I haven't been able to find a solution for iOS. It looks like iOS doesn't have any kind of error property at all. Any pointers anyone??