如何从其父级调用组件的公共方法？

Question

因此，我想在子组件（TimeEntryForm）中调用OpenModal（）方法。我认为我需要访问TimeEntryForm组件的实例，但是我不知道如何创建TimeEntryForm的命名实例。

任何帮助将不胜感激。

父组件

<button type="button" onclick="@TimeEntryForm.OpenModal()" class="btn btn-info btn-lg">
    <span class="glyphicon glyphicon-plus"></span> Add
</>

<TimeEntryForm></TimeEntryForm>

TimeEntry子组件

@using Chopper.Shared
@using DatabaseModel.Models
@page "/timeentryform"
@inject HttpClient HTTP
@inherits TimeEntryFormModel

@if (IsOpened)
{
    <div class="modal" role="dialog" tabindex="-1" style="display: block;">
        <div class="modal-dialog modal-dialog-centered" role="document">
            <div class="modal-content">
                <div class="modal-header">
                    <h5 class="modal-title">Add a Time Entry</h5>
                </div>
                <div class="modal-body">

                    <form>
                        <div class="form-group">
                            <label for="Job" class="col-form-label">Job:</label>
                            <input type="text" class="form-control" />
                        </div>
                        <div class="form-group">
                            <label for="Employee" class="col-form-label">Employee:</label>
                            <input class="form-control" type="text" />
                        </div>
                        <div class="form-group">
                            <label for="Hours" class="col-form-label">Hours:</label>
                            <input class="form-control" type="text" />
                        </div>
                    </form>

                </div>
                <div class="modal-footer">
                    <button type="button" class="btn btn-primary" onclickAsync="@OnAddTimeEntry()">Add Entry</button>
                    <button type="button" class="btn btn-primary" onclick="@CloseModal">Close</button>
                </div>
            </div>
        </div>
    </div>
    <div class="modal-backdrop show"></div>
}

视图模型后面的时间输入子组件代码

using Chopper.Client.TimeEntries.Services;
using DatabaseModel.Models;
using Microsoft.AspNetCore.Blazor.Components;
using System.Threading.Tasks;

namespace Chopper.Client.TimeEntries
{
    public class TimeEntryFormModel : BlazorComponent
    {
        protected TimeEntry TimeEntry = new TimeEntry();

        [Inject]
        private TimeEntriesServices _client { get; set; }

        protected bool IsOpened { get; set; }

        public void OpenModal()
        {
            IsOpened = true;
            StateHasChanged();
        }

        //[Parameter]
        protected void CloseModal()
        {
            IsOpened = false;
            StateHasChanged();
        }

        protected async Task OnAddTimeEntry()
        {

            if (TimeEntry.Job != null && TimeEntry.Category != null && TimeEntry.TimeSpentHours > 0 && TimeEntry.Employee != null)
            {
                await _client.CreateTimeEntry(TimeEntry);
                await OnInitAsync();
                StateHasChanged();
                //return true;
            }
            //return false;
        }

    }
}

Answer 1

所以我需要在protected TimeEntryForm timeEntryForm = new TimeEntryForm();的父组件模型中添加一个受保护的成员

，然后在视图中将其引用为<TimeEntryForm ref="timeEntryForm"></TimeEntryForm>

父组件

<button type="button" onclick="@timeEntryForm.OpenModal()" class="btn btn-info btn-lg">
    <span class="glyphicon glyphicon-plus"></span> Add
</>

<TimeEntryForm ref="timeEntryForm"></TimeEntryForm>

模型/视图模型后面的父组件代码

public class TimeEntriesGridModel : BlazorComponent
{
    [Inject]
    private TimeEntriesServices _client { get; set; }

    protected TimeEntryForm timeEntryForm; // = new TimeEntryForm(); //Per Kirk Woll's suggestion

    protected List<TimeEntry> Model { get; set; }

    protected override async Task OnInitAsync()
    {
        Model = await _client.GetAllTimeEntries();
    }


}

TimeEntry子组件

@using Chopper.Shared
@using DatabaseModel.Models
@page "/timeentryform"
@inject HttpClient HTTP
@inherits TimeEntryFormModel

@if (IsOpened)
{
    <div class="modal" role="dialog" tabindex="-1" style="display: block;">
        <div class="modal-dialog modal-dialog-centered" role="document">
            <div class="modal-content">
                <div class="modal-header">
                    <h5 class="modal-title">Add a Time Entry</h5>
                </div>
                <div class="modal-body">

                    <form>
                        <div class="form-group">
                            <label for="Job" class="col-form-label">Job:</label>
                            <input type="text" class="form-control" />
                        </div>
                        <div class="form-group">
                            <label for="Employee" class="col-form-label">Employee:</label>
                            <input class="form-control" type="text" />
                        </div>
                        <div class="form-group">
                            <label for="Hours" class="col-form-label">Hours:</label>
                            <input class="form-control" type="text" />
                        </div>
                    </form>

                </div>
                <div class="modal-footer">
                    <button type="button" class="btn btn-primary" onclickAsync="@OnAddTimeEntry()">Add Entry</button>
                    <button type="button" class="btn btn-primary" onclick="@CloseModal">Close</button>
                </div>
            </div>
        </div>
    </div>
    <div class="modal-backdrop show"></div>
}

视图模型后面的时间输入子组件代码

using Chopper.Client.TimeEntries.Services;
using DatabaseModel.Models;
using Microsoft.AspNetCore.Blazor.Components;
using System.Threading.Tasks;

namespace Chopper.Client.TimeEntries
{
    public class TimeEntryFormModel : BlazorComponent
    {
        protected TimeEntry TimeEntry = new TimeEntry();

        [Inject]
        private TimeEntriesServices _client { get; set; }

        protected bool IsOpened { get; set; }

        public void OpenModal()
        {
            IsOpened = true;
            StateHasChanged();
        }

        //[Parameter]
        protected void CloseModal()
        {
            IsOpened = false;
            StateHasChanged();
        }

        protected async Task OnAddTimeEntry()
        {

            if (TimeEntry.Job != null && TimeEntry.Category != null && TimeEntry.TimeSpentHours > 0 && TimeEntry.Employee != null)
            {
                await _client.CreateTimeEntry(TimeEntry);
                await OnInitAsync();
                StateHasChanged();
                //return true;
            }
            //return false;
        }

    }
}

EIA：

根据Kirk Woll的建议删除了timeEntryForm初始化后的代码。

Answer 2

同志，   请，请按照下列步骤操作：   1.在父组件中定义一个事件委托，该委托的对象是告诉孩子      组件以打开模式窗口：    public event Action OnOpenModal;   2.在父组件中定义一个调用事件委托的方法   private void OpenMe() => OnOpenModal?.Invoke();  3.当用户单击父组件中定义的按钮时，将调用此方法：     注意：不要在OpenMe之后使用括号      <button type="button" onclick="@OpenMe" class="btn btn-info btn-lg"> <span class="glyphicon glyphicon-plus"></span> Add </>  4.使用事件委托的值向子组件元素添加属性MyModal。      <TimeEntryForm MyModal = "@OnOpenModal"></TimeEntryForm>

 Define a property of Action delegate to store the event delegate passed to the Child Component




[Parameter] protected Action MyModal { get; set; }


    protected override void OnInit()
    {
        // Attach the OpenModal method defined in the Child // Component to the delegate
        MyModal += OpenModal;
    }

 Now, whenever the user hit the button the OpenModal is called and the modal window 
 is displayed. 

public void OpenModal()


 {
            IsOpened = true;
            StateHasChanged();
     }