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我在学习Salesforce.com的Apex编程语言，我在这里有一些代码来自Jason Ouellette编写的“Force.com平台开发”一书。我仍然在学习基础知识，请耐心等待。为了将上面的代码放在上下文中，我们在本书中有一个服务管理器示例应用程序，我正在检查他们写的Apex触发器设备，以确保时间卡具有有效的分配。分配是一个记录，表示某个资源在某个时间段内在某个项目上配备了人员。顾问（又名资源）只能为他或她有权工作的项目和时间段输入时间卡。 Resource_c是Assignment_c和Timecard_c对象的父级。Elementary Apex Trigger Logic Breakdown
所以这里是他们给我的触发器和相应的apex类的代码。 我一直试图分解它并逐行评论/提问，以便理解它的逻辑。不过，我仍然错过了一些基础知识，随时可以帮助我解读这一点。
5-57触发
trigger validateTimecard on Timecard__c (before insert, before update) {
TimecardManager.handleTimecardChange(Trigger.old, Trigger.new);
// TheApexClass.methodThatDoesWork(variable, variable)
// So there are 2 parameters which are 2 lists, Trigger.old and Trigger.new.
// Which means, when this method is called it needs these 2 lists
// to process it's block of code, right?
// Why are they called Trigger.old, Trigger.new? Does the order of variables matter?
}
5-58 - 雍雅轩类 - 这确实验证代表触发的考勤卡的工作。
public class TimecardManager {
public class TimecardException extends Exception {}
public static void handleTimecardChange(List<Timecard__c> oldTimecards, List<Timecard__c> newTimecards) {
// Identifying 2 lists of Timecards as parameters, oldTimecards and newTimecards
// within the class. How is this associated with the trigger parameters
// that were seen in the trigger above. Are they the same parameters with
// different names? Why are they named differently here? Is it better to
// write the trigger first, or the apex class first?
Set<ID> resourceIds = new Set<ID>(); // making a new set of primitive data type ID called resourceIds
for (Timecard__c timecard : newTimecards) {
// This for loop assigns the timecard variable record to the list of newTimecards
// and then executes the block of code below for each.
// The purpose of this is to identify all the resources that have timecards.
resourceIds.add(timecard.Resource__c);
// It does this by adding the Timecard_c's relationship ID from each parent record Resource_c to the resourceIds set.
// For clarification, Resource_c is a parent to both
// Assignment_c and Timecard_c objects. Within the Timecard_c object, Resource_c
// is a Master-Detail data type. Is there a relationship ID that is created
// for the relationship between Resource_c and Timecard_c?
}
List<Assignment__c> assignments = [ SELECT Id, Start_Date__c, End_Date__c, Resource__c FROM Assignment__c WHERE Resource__c IN :resourceIds ];
// The purpose of this is to make a list of selected information from Assignments_c that have resources with timecards.
if (assignments.size() == 0) {
// If there isn't a Resource_c from Assignments_c that matches a Resource_c that has a Timecard_c,
throw new TimecardException('No assignments'); // then an exception is thrown.
}
Boolean hasAssignment; // creation of a new Boolean variable
for (Timecard__c timecard : newTimecards) { // so for every newTimecards records,
hasAssignment = false; // set Boolean to false as default,
for (Assignment__c assignment : assignments) { // check through the assignments list
if (assignment.Resource__c == timecard.Resource__c && // to make sure the Resources match,
timecard.Week_Ending__c - 6 >= assignment.Start_Date__c && // the end of the timecard is greater than the assignment's start date,
timecard.Week_Ending__c <= assignment.End_Date__c) { // and the end of the timecard is before the assignment's end date.
hasAssignment = true; // if these all 3 are correct, than the Timecard does in fact have an assignment.
break; // exits the loop
}
}
if (!hasAssignment) { // if hasAssignment is false then,
timecard.addError('No assignment for resource ' + // display an error message
timecard.Resource__c + ', week ending ' +
timecard.Week_Ending__c);
}
}
}
}
谢谢你的帮助。