批评我简单的 MVP Winforms 应用程序 [英] Critique my simple MVP Winforms app
问题描述
我正在努力思考 C#/Winforms 应用程序中使用的 MVP 模式.所以我创建了一个简单的记事本"之类的应用程序来尝试解决所有细节.我的目标是创建一些可以执行打开、保存、新建以及在标题栏中反映已保存文件名称的经典 Windows 行为的东西.此外，当有未保存的更改时，标题栏应包含一个 *.
I'm trying to wrap my mind around the MVP pattern used in a C#/Winforms app. So I created a simple "notepad" like application to try to work out all the details. My goal is to create something that does the classic windows behaviors of open, save, new as well as reflecting the name of the saved file in the title bar. Also, when there are unsaved changes, the title bar should include an *.
所以我创建了一个视图 &管理应用程序持久状态的演示者.我考虑过的一项改进是打破文本处理代码，使视图/展示器真正成为一个单一用途的实体.
So I created a view & a presenter that manage the application's persistence state. One improvement I've considered is breaking out the text handling code so the view/presenter is truly a single-purpose entity.
这是一个屏幕截图供参考......
Here is a screen shot for reference ...
我在下面包含了所有相关文件.我对有关我是否以正确的方式完成它或是否有改进方法的反馈感兴趣.
I'm including all of the relevant files below. I'm interested in feedback about whether I've done it the right way or if there are ways to improve.
NoteModel.cs:
NoteModel.cs:
public class NoteModel : INotifyPropertyChanged
{
public string Filename { get; set; }
public bool IsDirty { get; set; }
string _sText;
public readonly string DefaultName = "Untitled.txt";
public string TheText
{
get { return _sText; }
set
{
_sText = value;
PropertyHasChanged("TheText");
}
}
public NoteModel()
{
Filename = DefaultName;
}
public void Save(string sFilename)
{
FileInfo fi = new FileInfo(sFilename);
TextWriter tw = new StreamWriter(fi.FullName);
tw.Write(TheText);
tw.Close();
Filename = fi.FullName;
IsDirty = false;
}
public void Open(string sFilename)
{
FileInfo fi = new FileInfo(sFilename);
TextReader tr = new StreamReader(fi.FullName);
TheText = tr.ReadToEnd();
tr.Close();
Filename = fi.FullName;
IsDirty = false;
}
private void PropertyHasChanged(string sPropName)
{
IsDirty = true;
PropertyChanged.Invoke(this, new PropertyChangedEventArgs(sPropName));
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
#endregion
}
Form2.cs:
public partial class Form2 : Form, IPersistenceStateView
{
PersistenceStatePresenter _peristencePresenter;
public Form2()
{
InitializeComponent();
}
#region IPersistenceStateView Members
public string TheText
{
get { return this.textBox1.Text; }
set { textBox1.Text = value; }
}
public void UpdateFormTitle(string sTitle)
{
this.Text = sTitle;
}
public string AskUserForSaveFilename()
{
SaveFileDialog dlg = new SaveFileDialog();
DialogResult result = dlg.ShowDialog();
if (result == DialogResult.Cancel)
return null;
else
return dlg.FileName;
}
public string AskUserForOpenFilename()
{
OpenFileDialog dlg = new OpenFileDialog();
DialogResult result = dlg.ShowDialog();
if (result == DialogResult.Cancel)
return null;
else
return dlg.FileName;
}
public bool AskUserOkDiscardChanges()
{
DialogResult result = MessageBox.Show("You have unsaved changes. Do you want to continue without saving your changes?", "Disregard changes?", MessageBoxButtons.YesNo);
if (result == DialogResult.Yes)
return true;
else
return false;
}
public void NotifyUser(string sMessage)
{
MessageBox.Show(sMessage);
}
public void CloseView()
{
this.Dispose();
}
public void ClearView()
{
this.textBox1.Text = String.Empty;
}
#endregion
private void btnSave_Click(object sender, EventArgs e)
{
_peristencePresenter.Save();
}
private void btnOpen_Click(object sender, EventArgs e)
{
_peristencePresenter.Open();
}
private void btnNew_Click(object sender, EventArgs e)
{
_peristencePresenter.CleanSlate();
}
private void Form2_Load(object sender, EventArgs e)
{
_peristencePresenter = new PersistenceStatePresenter(this);
}
private void Form2_FormClosing(object sender, FormClosingEventArgs e)
{
_peristencePresenter.Close();
e.Cancel = true; // let the presenter handle the decision
}
private void textBox1_TextChanged(object sender, EventArgs e)
{
_peristencePresenter.TextModified();
}
}
IPersistenceStateView.cs
IPersistenceStateView.cs
public interface IPersistenceStateView
{
string TheText { get; set; }
void UpdateFormTitle(string sTitle);
string AskUserForSaveFilename();
string AskUserForOpenFilename();
bool AskUserOkDiscardChanges();
void NotifyUser(string sMessage);
void CloseView();
void ClearView();
}
PersistenceStatePresenter.cs
PersistenceStatePresenter.cs
public class PersistenceStatePresenter
{
IPersistenceStateView _view;
NoteModel _model;
public PersistenceStatePresenter(IPersistenceStateView view)
{
_view = view;
InitializeModel();
InitializeView();
}
private void InitializeModel()
{
_model = new NoteModel(); // could also be passed in as an argument.
_model.PropertyChanged += new PropertyChangedEventHandler(_model_PropertyChanged);
}
private void InitializeView()
{
UpdateFormTitle();
}
private void _model_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
if (e.PropertyName == "TheText")
_view.TheText = _model.TheText;
UpdateFormTitle();
}
private void UpdateFormTitle()
{
string sTitle = _model.Filename;
if (_model.IsDirty)
sTitle += "*";
_view.UpdateFormTitle(sTitle);
}
public void Save()
{
string sFilename;
if (_model.Filename == _model.DefaultName || _model.Filename == null)
{
sFilename = _view.AskUserForSaveFilename();
if (sFilename == null)
return; // user canceled the save request.
}
else
sFilename = _model.Filename;
try
{
_model.Save(sFilename);
}
catch (Exception ex)
{
_view.NotifyUser("Could not save your file.");
}
UpdateFormTitle();
}
public void TextModified()
{
_model.TheText = _view.TheText;
}
public void Open()
{
CleanSlate();
string sFilename = _view.AskUserForOpenFilename();
if (sFilename == null)
return;
_model.Open(sFilename);
_model.IsDirty = false;
UpdateFormTitle();
}
public void Close()
{
bool bCanClose = true;
if (_model.IsDirty)
bCanClose = _view.AskUserOkDiscardChanges();
if (bCanClose)
{
_view.CloseView();
}
}
public void CleanSlate()
{
bool bCanClear = true;
if (_model.IsDirty)
bCanClear = _view.AskUserOkDiscardChanges();
if (bCanClear)
{
_view.ClearView();
InitializeModel();
InitializeView();
}
}
}
推荐答案
接近完美 MVP 被动视图模式的唯一方法是为对话框编写自己的 MVP 三元组，而不是使用 WinForms 对话框.然后您可以将对话框创建逻辑从视图移动到演示者.
The only way to get any closer to a perfect MVP passive view pattern would be to write your own MVP triads for the dialogs instead of using the WinForms dialogs. Then you could move the dialog creation logic from the view to the presenter.
这进入了 mvp 黑社会之间的交流话题，这个话题在检查这种模式时通常会被忽略.我发现对我有用的是将黑社会与他们的演示者联系起来.
This gets into the topic of communication between mvp triads, a topic which is usually glossed over when examining this pattern. What I've found works for me is to connect triads at their presenters.
public class PersistenceStatePresenter
{
...
public Save
{
string sFilename;
if (_model.Filename == _model.DefaultName || _model.Filename == null)
{
var openDialogPresenter = new OpenDialogPresenter();
openDialogPresenter.Show();
if(!openDialogPresenter.Cancel)
{
return; // user canceled the save request.
}
else
sFilename = openDialogPresenter.FileName;
...
Show() 方法当然负责显示一个未提及的 OpenDialogView，它将接受用户输入并将其传递给 OpenDialogPresenter.无论如何，应该开始清楚演示者是一个精心设计的中间人.在不同的情况下，您可能会想重构一个中间人，但这里是有意的:
The Show() method, of course, is responsible for showing an unmentioned OpenDialogView, which would accept the users input and pass it along to the OpenDialogPresenter. In any case, it should be starting to become clear that a presenter is an elaborate middleman. Under different circumstances, you might be tempted to refactor a middleman out but here its is intentional to:
- 将逻辑排除在视图之外，因为它更难测试
- 避免视图和模型之间的直接依赖
有时我也看到了用于 MVP 三合会交流的模型.这样做的好处是演示者不需要知道彼此的存在.它通常通过在模型中设置一个状态来完成，该状态触发一个事件，然后另一个演示者监听.一个有趣的想法.我个人没有使用过的一种.
At times I've also seen the model used for MVP triad communication. The benefit of this is the presenter's don't need to know each other exist. Its usually accomplished by setting a state in the model, which triggers an event, which another presenter then listens for. An interesting idea. One I've not used personally.
以下是一些其他人用来处理三合会交流的一些技巧的链接:
Here's a few links with some of the techniques others have used to deal with triad communication:
- http://www.rickardnilsson.net/post/The-Humble-dialog-v2.aspx
- http://spin.atomicobject.com/2008/01/30/presenter-first-get-your-triads-talking/
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