Apex - 接口

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接口就像一个 Apex 类，其中没有实现任何方法。它只包含方法签名，但每个方法的主体是空的。要使用接口，另一个类必须通过为接口中包含的所有方法提供主体来实现它。

接口主要用于为代码提供抽象层。它们将方法的实现与声明分开。

让我们以我们的化工公司为例。假设我们需要向高级客户和普通客户提供折扣，并且两者的折扣会有所不同。

我们将创建一个名为DiscountProcessor的接口。

// Interface
public interface DiscountProcessor {
   Double percentageDiscountTobeApplied(); // method signature only
}

// Premium Customer Class
public class PremiumCustomer implements DiscountProcessor {
   
   //Method Call
   public Double percentageDiscountTobeApplied () {
      
      // For Premium customer, discount should be 30%
      return 0.30;
   }
}

// Normal Customer Class
public class NormalCustomer implements DiscountProcessor {
   
   // Method Call
   public Double percentageDiscountTobeApplied () {
      
      // For Premium customer, discount should be 10%
      return 0.10;
   }
}

当您实现接口时，必须实现该接口的方法。如果不实现接口方法，就会抛出错误。当您想让开发人员强制执行方法时，您应该使用接口。

Batch Apex 的标准 Salesforce 界面

SFDC 确实有 Database.Batchable、Schedulable 等标准接口。例如，如果实现 Database.Batchable 接口，则必须实现接口中定义的三个方法 - Start、Execute 和 Finish。

下面是标准 Salesforce 提供的 Database.Batchable 接口的示例，该接口向用户发送带有批处理状态的电子邮件。该接口有 3 个方法，Start、Execute 和 Finish。使用此接口，我们可以实现 Batchable 功能，并且它还提供 BatchableContext 变量，我们可以使用该变量来获取有关正在执行的 Batch 的更多信息并执行其他功能。

global class CustomerProessingBatch implements Database.Batchable<sobject7>,
Schedulable {
   // Add here your email address
   global String [] email = new String[] {'test@test.com'};

   // Start Method
   global Database.Querylocator start (Database.BatchableContext BC) {
      
      // This is the Query which will determine the scope of Records and fetching the same
      return Database.getQueryLocator('Select id, Name, APEX_Customer_Status__c,
         APEX_Customer_Decscription__c From APEX_Customer__c WHERE createdDate = today
         && APEX_Active__c = true');
   }

   // Execute method
   global void execute (Database.BatchableContext BC, List<sobject> scope) {
      List<apex_customer__c> customerList = new List<apex_customer__c>();
      List<apex_customer__c> updtaedCustomerList = new List<apex_customer__c>();
      
      for (sObject objScope: scope) {
         // type casting from generic sOject to APEX_Customer__c
         APEX_Customer__c newObjScope = (APEX_Customer__c)objScope ;
         newObjScope.APEX_Customer_Decscription__c = 'Updated Via Batch Job';
         newObjScope.APEX_Customer_Status__c = 'Processed';
         
         // Add records to the List
         updtaedCustomerList.add(newObjScope);
      }

      // Check if List is empty or not
      if (updtaedCustomerList != null && updtaedCustomerList.size()>0) {
         
         // Update the Records
         Database.update(updtaedCustomerList); System.debug('List Size
            '+updtaedCustomerList.size());
      }
   }

   // Finish Method
   global void finish(Database.BatchableContext BC) {
      Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
      
      // get the job Id
      AsyncApexJob a = [Select a.TotalJobItems, a.Status, a.NumberOfErrors,
      a.JobType, a.JobItemsProcessed, a.ExtendedStatus, a.CreatedById,
      a.CompletedDate From AsyncApexJob a WHERE id = :BC.getJobId()];
      System.debug('$$$ Jobid is'+BC.getJobId());
      
      // below code will send an email to User about the status
      mail.setToAddresses(email);
     
      // Add here your email address
      mail.setReplyTo('test@test.com');
      mail.setSenderDisplayName('Apex Batch Processing Module');
      mail.setSubject('Batch Processing '+a.Status);
      mail.setPlainTextBody('The Batch Apex job processed
         '+a.TotalJobItems+'batches with '+a.NumberOfErrors+'failures'+'Job Item
         processed are'+a.JobItemsProcessed);
      Messaging.sendEmail(new Messaging.Singleemailmessage [] {mail});
   }

   // Scheduler Method to scedule the class
   global void execute(SchedulableContext sc) {
      CustomerProessingBatch conInstance = new CustomerProessingBatch();
      database.executebatch(conInstance,100);
   }
}

要执行此类，您必须在开发人员控制台中运行以下代码。

CustomerProessingBatch objBatch = new CustomerProessingBatch ();
Database.executeBatch(objBatch);