场景描述：开发中经常遇到记录一旦创建，其中的某个字段就不允许被修改的需求，以保证记录的安全性，以下提供两种解决方案。
方案一：使用Validation Rules实现 Sample：当记录第一次被保存后，就不允许用户修改其中某个字段-isCheck:
Validation Rule:
最终效果：
方案二：使用Trigger实现
Sample：比较old和new fields是否相同：oldMap适用于Update/Delete trigger
for(Opportunity opp : Trigger.new){ //Create an old and new map so that we can compare values Opportunity oldOpp = Trigger.oldMap.get(opp.ID); Opportunity newOpp = Trigger.newMap.get(opp.ID); //Retrieve the old and new Reseller Email Field string oldResellerEmail = oldOpp.Reseller_Email__c; string newResellerEmail = newOpp.Reseller_Email__c; //If the fields are different, the email has changed if(oldResellerEmail != newResellerEmail){ oppIDs.put(opp.Id,opp.Reseller_Email__c); } }注意：在实际运用时，可能会出现下图错误： 我们仅需改进如下：
((Map<Id, Lead>)Trigger.oldMap).get(l.Id).OwnerId <> l.OwnerId【Trigger项目实战 - after insert/update/delete/undelete】：
项目中有如下需求：A和B对象为lookup关系，其中A为父，B为子，目前想将B的Name字段拼接到A的某字段上，Code如下：
public class TradingAccountTriggerFunction { public static void joinLoginToAccount(Set<String> accSet) { Savepoint sp = Database.setSavepoint(); try{ List<Account> accs = [SELECT Id, Trading_Account_Login__c, (SELECT Id, Name FROM MT4_Accounts__r ORDER BY LastModifiedDate) FROM Account WHERE Id IN :accSet]; for(Account acc : accs) { acc.Trading_Account_Login__c = ''; for(Integer i = 0; i < acc.MT4_Accounts__r.size(); i++) { acc.Trading_Account_Login__c += (i == acc.MT4_Accounts__r.size() - 1) ? acc.MT4_Accounts__r[i].Name : acc.MT4_Accounts__r[i].Name + ';'; System.debug(acc.Trading_Account_Login__c); } } update accs; }catch(Exception e) { System.debug(e.getMessage()); Database.rollback(sp); } } } public class TradingAccountTriggerHandler extends TriggerHandler{ //handle before insert logic public override void beforeInsert(){} //handle before update logic public override void beforeUpdate(){} //handle before delete logic public override void beforeDelete(){} //handle after insert logic public override void afterInsert(){ System.debug('go into after insert logic.'); Set<String> accIdSet = new Set<String>(); for(MT4_Accounts__c tAcc : (List<MT4_Accounts__c>)Trigger.new) { accIdSet.add(tAcc.Account__c); } if(accIdSet.size() > 0) { TradingAccountTriggerFunction.joinLoginToAccount(accIdSet); } } //handle after update logic public override void afterUpdate(){ System.debug('go into after update logic.'); Set<String> accIdSet = new Set<String>(); for(MT4_Accounts__c tAcc : (List<MT4_Accounts__c>)Trigger.new) { if(((Map<Id, MT4_Accounts__c>)Trigger.oldMap).get(tAcc.Id).Name <> tAcc.Name) accIdSet.add(tAcc.Account__c); } if(accIdSet.size() > 0) { TradingAccountTriggerFunction.joinLoginToAccount(accIdSet); } } //handle after delete logic public override void afterDelete(){ System.debug('go into after delete logic.'); Set<String> accIdSet = new Set<String>(); for(MT4_Accounts__c tAcc : (List<MT4_Accounts__c>)Trigger.old) { accIdSet.add(tAcc.Account__c); } if(accIdSet.size() > 0) { TradingAccountTriggerFunction.joinLoginToAccount(accIdSet); } } //handle after undelete logic public override void afterUndelete(){ System.debug('go into after undelete logic.'); Set<String> accIdSet = new Set<String>(); for(MT4_Accounts__c tAcc : (List<MT4_Accounts__c>)Trigger.new) { accIdSet.add(tAcc.Account__c); } if(accIdSet.size() > 0) { TradingAccountTriggerFunction.joinLoginToAccount(accIdSet); } } }
