[英]How to resolve a dependency in IValueConverter in Xamarin.Forms using Prism/DryIoC
我有一個使用Prism和DryIoC作為容器的Xamarin.Forms應用程序。 我有一個值轉換器,我需要使用我通過IContainerRegistry注冊的服務。
containerRegistry.RegisterSingleton<IUserService, UserService>();
如何解決這種依賴關系而不必求助於構造函數注入,因為IValueConverter是由XAML而不是DryIoC構造的? 我可以在Prism / DryIoC中使用服務定位器嗎? 如果是這樣,怎么樣?
以下是值轉換器代碼:
public class MyValueConverter : IValueConverter
{
private readonly IUserService _userService;
public MyValueConverter()
{
// Ideally, I can use a service locator here to resolve IUserService
//_userService = GetContainer().Resolve<IUserService>();
}
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var isUserLoggedIn = _userService.IsLoggedIn;
if (isUserLoggedIn)
// Do some conversion
else
// Do some other conversion
...
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
我鼓勵您更新到7.1預覽版,因為它解決了這個問題。 你的轉換器就像是:
public class MyValueConverter : IValueConverter
{
private readonly IUserService _userService;
public MyValueConverter(IUserService userService)
{
_userService = userService;
}
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var isUserLoggedIn = _userService.IsLoggedIn;
if (isUserLoggedIn)
// Do some conversion
else
// Do some other conversion
...
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
然后您的XAML看起來像:
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:converters="clr-namespace:DemoApp.Converters"
xmlns:ioc="clr-namespace:Prism.Ioc;assembly=Prism.Forms"
x:Class="DemoApp.Views.AwesomePage">
<ContentPage.Resources>
<ioc:ContainerProvider x:TypeArguments="converters:MyValueConverter"
x:Key="myValueConverter" />
</ContentPage.Resources>
</ContentPage>
請務必在更新之前查看發行說明 ,因為該版本還包含一些重大更改。
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