我刚开始学习C#.我看到一个老问题,有人试图制作可口可乐机器,这似乎是一个很好的练习.
但我陷入了金钱按钮.我无法弄清楚如何存储按钮在变量中所代表的金额,可通过ColaMachine方法访问.
我有以下代码:
using System;
using System.Windows.Forms;
using System.Drawing;
namespace QuickSharp
{
public class ColaMachine : Form
{
public ColaMachine()
{
this.Text = "Cola Machine";
this.Size = new Size(450 , 500);
//Money & Money Buttons
Label Money;
Money = new Label();
Money.Text = "Insert Coins Here:";
Money.Location = new Point(20, 100);
this.Controls.Add(Money);
Button MoneyButton1;
MoneyButton1 = new Button();
MoneyButton1.Text = "€0,05";
MoneyButton1.Location = new Point(28,125);
MoneyButton1.Click += new System.EventHandler(this.MoneyButton1_Click);
this.Controls.Add(MoneyButton1);
Button MoneyButton2;
MoneyButton2 = new Button();
MoneyButton2.Text = "€0,10";
MoneyButton2.Location = new Point(28,165);
MoneyButton2.Click += new System.EventHandler(this.MoneyButton2_Click);
this.Controls.Add(MoneyButton2);
Button MoneyButton3;
MoneyButton3 = new Button();
MoneyButton3.Text = "€0,20";
MoneyButton3.Location = new Point(28,205);
MoneyButton3.Click += new System.EventHandler(this.MoneyButton3_Click);
this.Controls.Add(MoneyButton3);
Button MoneyButton4;
MoneyButton4 = new Button();
MoneyButton4.Text = "€0,50";
MoneyButton4.Location = new Point(28,245);
MoneyButton4.Click += new System.EventHandler(this.MoneyButton4_Click);
this.Controls.Add(MoneyButton4);
Button MoneyButton5;
MoneyButton5 = new Button();
MoneyButton5.Text = "€1,00";
MoneyButton5.Location = new Point(28,285);
MoneyButton5.Click += new System.EventHandler(this.MoneyButton5_Click);
this.Controls.Add(MoneyButton5);
Button MoneyButton6;
MoneyButton6 = new Button();
MoneyButton6.Text = "€2,00";
MoneyButton6.Location = new Point(28,325);
MoneyButton6.Click += new System.EventHandler(this.MoneyButton6_Click);
this.Controls.Add(MoneyButton6);
// Drinks & Drink Buttons
Label Drinks;
Drinks = new Label();
Drinks.Text = "Choose Your Drink:";
Drinks.Location = new Point(315 , 100);
Drinks.AutoSize = true;
this.Controls.Add(Drinks);
Button DrinkButton1;
DrinkButton1 = new Button();
DrinkButton1.Text = "Coca-Cola";
DrinkButton1.Location = new Point(328,125);
this.Controls.Add(DrinkButton1);
Button DrinkButton2;
DrinkButton2 = new Button();
DrinkButton2.Text = "Coca-Cola Light";
DrinkButton2.Location = new Point(328,165);
this.Controls.Add(DrinkButton2);
Button DrinkButton3;
DrinkButton3 = new Button();
DrinkButton3.Text = "Fanta";
DrinkButton3.Location = new Point(328,205);
this.Controls.Add(DrinkButton3);
Button DrinkButton4;
DrinkButton4 = new Button();
DrinkButton4.Text = "Sprite";
DrinkButton4.Location = new Point(328,245);
this.Controls.Add(DrinkButton4);
Button DrinkButton5;
DrinkButton5 = new Button();
DrinkButton5.Text = "Spa Blauw";
DrinkButton5.Location = new Point(328,285);
this.Controls.Add(DrinkButton5);
Button DrinkButton6;
DrinkButton6 = new Button();
DrinkButton6.Text = "Red Bull";
DrinkButton6.Location = new Point(328,325);
this.Controls.Add(DrinkButton6);
//Header & Machine Display
Label Header;
Header = new Label();
Header.Text = "Coca-Cola Machine";
Header.Font = new Font("Arial" , Header.Font.Size +5);
Header.ForeColor = Color.DarkRed;
Header.Location = new Point(132, 20);
Header.AutoSize = true;
this.Controls.Add(Header);
TextBox TextBox1 ;
TextBox1 = new TextBox();
if(InsertedCoins == 0.00)
TextBox1.Text = "Buy Your Ice Cold Drinks Here!";
else
TextBox1.Text = "Inserted Coins: €" + InsertedCoins;
TextBox1.BackColor = Color.Black;
TextBox1.ForeColor = Color.Red;
TextBox1.Font = new Font("Arial" , TextBox1.Font.Size +3);
TextBox1.ReadOnly = true;
TextBox1.Size = new Size(210,300);
TextBox1.Location = new Point(112,50);
// I tried to get the text scrolling here... :)
TextBox1.SelectionStart = TextBox1.Text.Length;
TextBox1.ScrollToCaret();
TextBox1.Refresh();
this.Controls.Add(TextBox1);
}
public double InsertedCoins;
// Money Button Click Events
private void MoneyButton1_Click(object sender, EventArgs e)
{
InsertedCoins = InsertedCoins + 0.05;
}
private void MoneyButton2_Click(object sender, EventArgs e)
{
InsertedCoins = InsertedCoins + 0.10;
}
private void MoneyButton3_Click(object sender, EventArgs e)
{
InsertedCoins = InsertedCoins + 0.20;
}
private void MoneyButton4_Click(object sender, EventArgs e)
{
InsertedCoins = InsertedCoins + 0.50;
}
private void MoneyButton5_Click(object sender, EventArgs e)
{
InsertedCoins = InsertedCoins + 1.00;
}
private void MoneyButton6_Click(object sender, EventArgs e)
{
InsertedCoins = InsertedCoins + 2.00;
}
private static void Main()
{
ColaMachine Scherm;
Scherm = new ColaMachine();
Application.Run(Scherm);
}
}
}
另外,如果您对我的一般编程有任何提示(例如,为了让其他人试图阅读我的代码更容易理解),请告诉我!
当我想到可乐机器时,我看到机器中每种饮料的按钮,但不是用于不同金额的按钮.也许你的意思是一个焦炭花费50美分所以按下我需要收取50美分的可乐按钮.
按钮和事件处理程序
当您按下屏幕上的按钮时,它会生成一个单击事件.您需要编写一个方法来响应该单击.我们用来响应事件的任何方法(一般来说)都称为事件处理程序.您必须告诉您的程序哪些按钮与哪些事件处理程序一起使用.我们称之为注册事件处理程序
按照惯例,如果您的按钮名为"CokeButton",则与该特定按钮关联的事件处理程序将命名为"CokeButton_ClickHandler".或类似的东西.
一般建议
想想你正在建模的东西,并在代码中定义事物以反映现实世界.模型中的东西通常最终会成为类,类属性和类字段.这些事情通常最终会成为适当类别中的方法.然后你想想这些事情是如何相互作用的.
在开始编写代码之前,您不需要弄清楚可乐机器的所有内容.你应该一次写一点点,测试那些,然后建立在你测试的东西上.不要编写复杂的交互代码然后进行测试.你最终会在追逐你的尾巴的圈子里旋转.写一点,测试一下,重复一遍.现在听我说,以后相信我; 写一点,测试一下,重复一遍.现在和永远听从这个建议.
所以这就是我对可乐机器的看法.首先是焦炭机本身.
public class CokeMachine {}
可乐机具有钱槽,返回槽和饮料按钮.我真的不能把钱放在一个插槽中,所以手边,我会说我会输入一个文本框.然后我会点击一个按钮,焦炭会分配.我觉得我已经定义了足够的模型来开始.关于可乐机器还有很多其他的东西,但我现在不会担心它们.
但我需要知道每种饮料的成本.
好吧,好吧.那么必须有"CokeCost","7UpCost"等字段.所以定义它们!我们将随时了解如何以及在何处使用它们.
public class CokeMachine {
Button Coke;
Button 7Up;
Button RootBeer;
TextBox MoneySlot;
double CokeCost = .75;
double 7UpCost = .65;
}
我说按钮需要处理程序,所以我们至少可以编写一些代码shell.我希望他们都能以同样的方式工作,所以我现在专注于一个.请注意,在编写代码时,我意识到必须处理的其他事情.我会发表评论,调用尚不存在的方法等.
public class CokeMachine {
Button Coke;
Button 7Up;
Button RootBeer;
TextBox MoneySlot;
double CokeCost = .75;
double 7UpCost = .65;
// "wiring up" the coke button click event to it's handler.
// We do this in C# by declaring an new EventHandler object (a .NET framework supplied class)
// and we pass in the name of our method as a parameter.
// This new EventHandler is *added* to the button's click event.
// An event can have multiple handlers, that's why we do "+="
// instead of just "=". Otherwise we would have accidentally "unhooked" any
// previously registered handlers.
Coke.Click += new EventHandler(Coke_ClickHandler);
// this is the .NET event handler method signature.
Public void Coke_ClickHandler (object sender, EventArgs args){
if (MoneySlot.Value >= CokeCost) {
DispenseDrink();
// How do I handle returning change? Maybe DispenseDrink() can do that.
}else {
// tell customer to put in more money
}
}
private void DispenseDrink() {
// An empty method is enough to get it to compile so for now that's fine.
// I need to test the Coke_EventHandler logic that I've written so far.
}
}
现在我需要测试到目前为止我写的内容.在那之后,我需要决定下一步要关注什么.但是要意识到,当你编写依赖于已编写代码的新代码时,如果现有代码尚未经过测试 - 现在你看到了错误,那么你自己就更难了.您可以在代码更简单时进行测试.现在还有更多,它更复杂,并且将更难调试和修复.
建议,第二部分
冒着把事搞砸的风险,我按照原来的答案提出这个问题:
你可以看到每个饮料按钮都做同样的事情,并且考虑到上面的代码,我们会为每个按钮一遍又一遍地编写相同的逻辑.如果有什么需要改变,我们必须在任何地方改变它.
更多一般建议
一个面向对象的Progamming启发式封装了保持不变的内容.你应该一直在寻找可能成为公共代码候选者的地方.
我想强调的是,这种常见的按钮行为对我来说并不是很明显.只有在我编写完上面的代码之后,我才开始认为所有的饮料按钮处理程序都会看起来一样,我意识到在真正的饮料机器上,它们实际上的行为方式相同.我的编码spidey-sense告诉它,当代码反映你真实事物的可识别行为(双关语意图!)时,这绝对是件好事.
重构
实际上是一个技术术语,意味着重新编写现有代码,使其更灵活,可重复使用,可读等.总之,可维护.
重构应始终在您的思维过程中.但请确保您有合理的理由进行任何更改.重塑代码是软件开发中不可或缺的一部分.
让我们通过提取方法来重构
Public void Coke_ClickHandler (object sender, EventArgs args){
PurchaseDrink("Coke", CokeCost);
}
// now we have a method that stands out and says THIS is how it works
// and a single point of change, rather than ump-teen button handlers.
private PurchaseDrink (string whatKind, double cost) {
// all I did so far is move the code and change "Cokecost" to "cost"
// Now I'm beginning to think I may need to pass "whatKind" to
// DispenseDrink() - but first I need to test the changes I've
// made at this level.
// ***** and since I already tested the code when I 1st wrote it,
// this refactoring will be easier & quicker to test.. GET IT??!! ******
if (MoneySlot.Value >= cost) {
DispenseDrink();
// How do I handle returning change? Maybe DispenseDrink() can do that.
}else {
// tell customer to put in more money
}
}
private void DispenseDrink() {
// An empty method is enough to get it to compile so for now that's fine.
// I need to test the Coke_EventHandler logic that I've written so far.
}
枚举
我讨厌使用字符串,就像我上面使用"可乐"一样.错字和套管(上/下,即)会导致Visual Studio无法捕获的问题.当我有一个有限的东西 - 各种饮料 - 我真的喜欢使用枚举.它们出现在intellesense中,我可以在switch语句中使用它们(并研究"类型安全"的概念).我真正喜欢的是,他们绝对在一个地方定义了我们的程序所知道的所有饮料类型.这就像文档!