C# Xamarin 避免代码重复

Question

我正在 Xamarin Studio 中使用 C# 制作一个基本的笔记应用程序，并且一直在学习在线课程。问题是提供的代码示例包含大量重复代码，这使得更新应用程序变得越来越困难。我在下面标记了与两个非常相似的classes，EditNoteViewController.cs和AddNoteViewController.cs有关的相关代码，我如何将代码提取出来以便我可以调用它一次？

或者，我正在考虑将其全部提取到一个 class 中，并根据用户是在创建还是更新笔记，使用条件流程呈现不同的属性。

EditNoteController.cs

using System;
using UIKit;

namespace NoteTaker.iOS
{
    public class EditNoteViewController : UIViewController
    {
        Note note;

        public EditNoteViewController (Note _note)
        {
            note = _note;
        }

        public override void ViewDidLoad ()
        {
            base.ViewDidLoad ();
            this.NavigationController.NavigationBar.BarTintColor = UIColor.FromRGB (255, 0, 255); // Repeated code. Also used in MainViewController.cs
            this.Title = "Edit Note";
            this.NavigationController.NavigationBar.TitleTextAttributes = new UIStringAttributes () { ForegroundColor = UIColor.White };

            this.NavigationController.NavigationBar.TintColor = UIColor.White;
            this.View.BackgroundColor = UIColor.White;


            var titleEntryBox = new UITextField () {
                Frame = new CoreGraphics.CGRect (0, 100, View.Bounds.Width, 45), // Repeated code
                BackgroundColor = UIColor.LightGray,
                TextColor = UIColor.Black,
                Text = note.title
            };

            var descriptionLabel = new UILabel () {
                Frame = new CoreGraphics.CGRect (10, 180, 250, 35),
                Text = "Description",
            };

            var descriptionEntryBox = new UITextView () {
                Frame = new CoreGraphics.CGRect (0, 220, View.Bounds.Width, 100), // Repeated code
                BackgroundColor = UIColor.LightGray,
                TextColor = UIColor.Black,
                Text = note.description
            };

            var updateButton = new UIButton () {
                Frame = new CoreGraphics.CGRect (10, 340, 120, 45)  
            }; // Repeated code

            updateButton.SetTitle ("Update", UIControlState.Normal);
            updateButton.BackgroundColor = UIColor.FromRGB (255, 0, 255);
            updateButton.SetTitleColor (UIColor.White, UIControlState.Normal);

            this.View.Add (titleEntryBox);
            this.View.Add (descriptionLabel);
            this.View.Add (descriptionEntryBox);
            this.View.Add (updateButton); 

            updateButton.TouchUpInside += (sender, e) => {
                if (titleEntryBox.Text.Length < 4)
                    return;
                var noteToUpdate = new Note () {
                    ID = note.ID,
                    title = titleEntryBox.Text,
                    description = descriptionEntryBox.Text,
                    dateCreated = DateTime.Now
                };
                Database.updateNote (noteToUpdate);

                this.NavigationController.PopViewController (true);
            };
        }
    }
}

AddNoteViewController.cs

using System;
using UIKit;

namespace NoteTaker.iOS
{
    public class AddNoteViewController : UIViewController
    {
        public AddNoteViewController () 
        {
        }

        public override void ViewDidLoad ()
        {
            base.ViewDidLoad ();
            this.NavigationController.NavigationBar.BarTintColor = UIColor.FromRGB (255, 0, 255);
            this.Title = "New Note";
            this.NavigationController.NavigationBar.TitleTextAttributes = new UIStringAttributes () { ForegroundColor = UIColor.White };

            this.NavigationController.NavigationBar.TintColor = UIColor.White;
            this.View.BackgroundColor = UIColor.White;

            var titleEntryBox = new UITextField () {
                Frame = new CoreGraphics.CGRect (0, 100, View.Bounds.Width, 45),
                BackgroundColor = UIColor.LightGray,
                Placeholder = "Enter title...",
                TextColor = UIColor.Black
            };

            var descriptionLabel = new UILabel () {
                Frame = new CoreGraphics.CGRect (10, 180, 250, 35),
                Text = "Enter description below"
            };

            var descriptionEntryBox = new UITextView () {
                Frame = new CoreGraphics.CGRect (0, 220, View.Bounds.Width, 100),
                BackgroundColor = UIColor.LightGray,
                TextColor = UIColor.Black
            };

            var saveButton = new UIButton () {
                Frame = new CoreGraphics.CGRect (10, 340, 120, 45)  
            };

            saveButton.SetTitle ("Save Note", UIControlState.Normal);
            saveButton.BackgroundColor = UIColor.FromRGB (255, 0, 255);
            saveButton.SetTitleColor (UIColor.White, UIControlState.Normal);

            this.View.Add (titleEntryBox);
            this.View.Add (descriptionLabel);
            this.View.Add (descriptionEntryBox);
            this.View.Add (saveButton); 

            saveButton.TouchUpInside += (sender, e) => {
                if (titleEntryBox.Text.Length < 4)
                    return;
                var noteToSave = new Note () {
                    title = titleEntryBox.Text,
                    description = descriptionEntryBox.Text,
                    dateCreated = DateTime.Now
                };
                Database.InsertNote (noteToSave);
                titleEntryBox.Text = "";
                descriptionEntryBox.Text = "";
            };
        }
    }
}

Answer 1

有很多不同的方法可以解决这样的问题；这只是一个简单的示例 - 将 null 传递到控制器将导致它成为 "Add"，否则它将充当 "Edit" 页面

public class NoteViewController : UIViewController
{
    Note note;

    public NoteViewController (Note _note)
    {
        note = _note;
    }

    public override void ViewDidLoad ()
    {
        base.ViewDidLoad ();
        this.NavigationController.NavigationBar.BarTintColor = UIColor.FromRGB (255, 0, 255); // Repeated code. Also used in MainViewController.cs

        this.Title = note == null ? "Add Note" : "Edit Note";

        this.NavigationController.NavigationBar.TitleTextAttributes = new UIStringAttributes () { ForegroundColor = UIColor.White };

        this.NavigationController.NavigationBar.TintColor = UIColor.White;
        this.View.BackgroundColor = UIColor.White;


        var titleEntryBox = new UITextField () {
            Frame = new CoreGraphics.CGRect (0, 100, View.Bounds.Width, 45), // Repeated code
            BackgroundColor = UIColor.LightGray,
            TextColor = UIColor.Black,
            Text = note == null ? string.Empty : note.title
        };

        var descriptionLabel = new UILabel () {
            Frame = new CoreGraphics.CGRect (10, 180, 250, 35),
            Text = "Description",
        };

        var descriptionEntryBox = new UITextView () {
            Frame = new CoreGraphics.CGRect (0, 220, View.Bounds.Width, 100), // Repeated code
            BackgroundColor = UIColor.LightGray,
            TextColor = UIColor.Black,
            Text = note == null ? string.Empty : note.description
        };

        var button = new UIButton () {
            Frame = new CoreGraphics.CGRect (10, 340, 120, 45)  
        }; // Repeated code

        if (note == null) {
          button.SetTitle ("Add", UIControlState.Normal);
        } else {
          button.SetTitle ("Update", UIControlState.Normal);
        }

        button.BackgroundColor = UIColor.FromRGB (255, 0, 255);
        button.SetTitleColor (UIColor.White, UIControlState.Normal);

        this.View.Add (titleEntryBox);
        this.View.Add (descriptionLabel);
        this.View.Add (descriptionEntryBox);
        this.View.Add (button); 

        button.TouchUpInside += (sender, e) => {

            if (note == null) {
            var noteToSave = new Note () {
                title = titleEntryBox.Text,
                description = descriptionEntryBox.Text,
                dateCreated = DateTime.Now
            };
            Database.InsertNote (noteToSave);
            titleEntryBox.Text = "";
            descriptionEntryBox.Text = "";

            } else {
            if (titleEntryBox.Text.Length < 4)
                return;
            var noteToUpdate = new Note () {
                ID = note.ID,
                title = titleEntryBox.Text,
                description = descriptionEntryBox.Text,
                dateCreated = DateTime.Now
            };
            Database.updateNote (noteToUpdate);
            this.NavigationController.PopViewController (true);
            }


        };
    }
}

C# Xamarin 避免代码重复

C# Xamarin avoiding code repetition

c#

refactoring

xamarin.ios

ios

xamarin