实例和实例之间往往需要共享一些数据(例如存款利率),将这些共享数据存放在每一个实例中显然不是什么好的办法,我们需要将它们抽取出来单独存放并被所有实例所“共享”,这就是Shared的来源,在C#语言中叫做Static。如下图所示:
using System ;public class Account{ private double balance = 0; private static double interest = 0.07; public void Withdraw(double amount) { balance -= amount; } public void Deposit(double amount) { balance += amount; } public static double InterestRate() { return interest; } public void ShowBalance() { Console.WriteLine("Current balance is {0}", balance); }}public class Client{ public static void Main() { Account account1 = new Account(); Account account2 = new Account(); account1.Deposit(10000); account2.Deposit(7000); account1.ShowBalance(); account2.ShowBalance(); Console.WriteLine("InterestRate is: {0}", Account.InterestRate()); }}
对于这类方法和属性我们在前面标示上Shared(VB.net)或static(C#),当看到这些标示后,我们就知道这些内容是用来被所有实例所共享的。这就算是Shared的起源吧。
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