Blazor通过反射获取嵌套组件 [英] Blazor get nested components by Reflection
问题描述
我实际上正在Blazor项目(0.8.0)中进行表单验证.
我创建了一个名为InputValidation的组件.该组件接收许多参数，以根据我们可以设置的条件测试属性值是否正确.
@using System.Linq.Expressions;
@typeparam TItem
@if (!Valid)
{
<span id="@(Id)_validation" class="form-text text-danger">@Message</span>
}
@functions {
[Parameter]
string Id { get; set; }
[Parameter]
TItem Property { get; set; }
[Parameter]
Expression<Func<TItem, bool>> On { get; set; }
[Parameter]
string Message { get; set; }
[Parameter]
bool ActiveOnLoad { get; set; } = true;
internal bool Valid { get; set; }
bool Activated;
protected async override Task OnInitAsync()
{
Activated = ActiveOnLoad;
}
protected async override Task OnAfterRenderAsync()
{
Activated = true;
}
protected async override Task OnParametersSetAsync()
{
Valid = !On.Compile().Invoke(Property);
}
}
您可以像这样在父组件上实现它:
<InputValidation Id="@nameof(ViewModel.UrlInput)" Property="@ViewModel.UrlInput" On="@(x => string.IsNullOrEmpty(x))" Message="Url is empty" ActiveOnLoad="@false"/>
我已经编写了一个类，用于验证所有InputValidation组件均具有
@if (ViewModel.IsValid(this))
此代表父组件.
问题是...它不起作用！
这是验证器的代码:
public static class ModelValidator
{
public static bool IsValid<T, V>(this T viewmodel, V component) where T : IViewModel where V : ComponentBase
=> component.GetType().GetFields().OfType<InputValidation<T>>().All(x => x.Valid);
}
我知道它不起作用，但是即使我们使用了反射(GetProperties，GetFields，GetMembers)，它也不会返回父组件的任何InputValidation成员.
我的问题是:有没有一种方法可以通过使用反射来获取所有子组件?如果是，该怎么办?
我知道Blazor仍处于早期阶段，我希望它会很快发布，因为它是一项非常令人愉快的技术！
感谢您的回复！
这里不需要反射(InputValidation组件不是父级中的字段，它是将由RenderTree呈现的组件)./p>
您可以使用ref属性捕获对每个InputValidation组件的引用.
<InputValidation ref="@InputValidationRef" Id="@nameof(ViewModel.UrlInput)" Property="@ViewModel.UrlInput" On="@(x => string.IsNullOrEmpty(x))" Message="Url is empty" ActiveOnLoad="@false"/>
通常，此引用"InputValidationRef"将是一个字段，但是您可以使用带有自定义设置器的属性来构建列表(或您喜欢的任何集合)
List<InputValidation> InputValidations = new List<InputValidation>();
InputValidation InputValidationRef { set => InputValidations.Add(value); }
因此，现在将每个InputValidation捕获为一个引用，并为每个InputValidationRef设置属性，该属性将依次将所有引用存储在"InputValidations"集合中.
现在，您有一个收藏夹，可以对其进行测试
InputValidations.All(iv => iv.Valid)
注意:该集合仅在呈现组件/页面之后填充，因此在初始页面加载期间，引用的集合为空，直到调用OnAfterRender/OnAfterRenderAsync方法为止.
I'm actually working on form validation in Blazor project (0.8.0).
I have created a component called InputValidation. This component receive many parameters to test if a property value is correct according a condition we can set up.
@using System.Linq.Expressions;
@typeparam TItem
@if (!Valid)
{
<span id="@(Id)_validation" class="form-text text-danger">@Message</span>
}
@functions {
[Parameter]
string Id { get; set; }
[Parameter]
TItem Property { get; set; }
[Parameter]
Expression<Func<TItem, bool>> On { get; set; }
[Parameter]
string Message { get; set; }
[Parameter]
bool ActiveOnLoad { get; set; } = true;
internal bool Valid { get; set; }
bool Activated;
protected async override Task OnInitAsync()
{
Activated = ActiveOnLoad;
}
protected async override Task OnAfterRenderAsync()
{
Activated = true;
}
protected async override Task OnParametersSetAsync()
{
Valid = !On.Compile().Invoke(Property);
}
}
You can implement it on your parent component like this :
<InputValidation Id="@nameof(ViewModel.UrlInput)" Property="@ViewModel.UrlInput" On="@(x => string.IsNullOrEmpty(x))" Message="Url is empty" ActiveOnLoad="@false"/>
I have coded a class that verifies that all InputValidation components have the property Valid at true.
@if (ViewModel.IsValid(this))
this represents the parent component.
The problem is... it's not working !
Here is the code of the validator :
public static class ModelValidator
{
public static bool IsValid<T, V>(this T viewmodel, V component) where T : IViewModel where V : ComponentBase
=> component.GetType().GetFields().OfType<InputValidation<T>>().All(x => x.Valid);
}
It's not working, I know, but even if we use Reflection (GetProperties, GetFields, GetMembers), it won't return any of the InputValidation members of the parent component.
My question is : is there a way to get all child components by using Reflection ? If yes, how to do it ?
I know that Blazor is still on early stage and I hope it will be released soon because it's a very pleasant technology !
Thank you for your responses !
You don't need reflection here (the InputValidation component is not a field in the parent, it is a component that will be rendered by the RenderTree).
You can capture a reference to each InputValidation component using the ref attribute.
<InputValidation ref="@InputValidationRef" Id="@nameof(ViewModel.UrlInput)" Property="@ViewModel.UrlInput" On="@(x => string.IsNullOrEmpty(x))" Message="Url is empty" ActiveOnLoad="@false"/>
Normally this ref "InputValidationRef" would be a field, but you can, instead use a property with a custom setter to build a list (or whatever collection you like)
List<InputValidation> InputValidations = new List<InputValidation>();
InputValidation InputValidationRef { set => InputValidations.Add(value); }
So, each InputValidation will now be captured as a reference and the Property InputValidationRef will be set for each one, which will, in turn, store all the references in the collection "InputValidations".
Now, you have a collection, you can test against
InputValidations.All(iv => iv.Valid)
Note: the collection is only populated after the component/page is rendered, so during the initial page load the collection of references is empty until the OnAfterRender/OnAfterRenderAsync method is called.
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