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clarification on Apex program
Hello there, As new to development, I referred a piece of code and trying to understand this program, some of the statements didn't understand where I put question mark
can anyone spare some time to explain once plz
//handler code -
public class NewClass { // class name
public static void NewMethod(List<Parent__c> newParent) { //created list using custom object parent and named it newParent
newParent = [SELECT Id, Name, Field1__c, Field2__c WHERE Id IN: newParent]; // fetching id, name and other fields where id is matching to newParent ? but with which other object they are comparing this ? are they fetching from newParent and assigning also in newParent ? plz explain this part
List<Child__c> childQry = new List<Child__c>(); // list created for child object
List<Child__c> childListToUpdate = new List<Child__c>(); //another list created for child object, did not understand why 2 list created here ?
for(Parent__c p : newParent) { // Parent object reference variable p created which will run through records saved in newParent list
childQry = [SELECT Id, Name, Parent__c, Field1__c, Field2__c FROM Child__c WHERE Field1__c =: p.Id]; // fetching records and assigning to list
for(Child__c c : childQry) { // loop running through childQry records
if(p.Id != null) { // null check
c.Field2__c = p.Field2__c; // assigning value to field2 from parent object field2
childListToUpdate.add(c); // inserting record in new list
}
}
}
update childListToUpdate; // updating the record, did not understand what is meaning of this, didn't we already insert record in previous line ?
}
}
//Trigger code
trigger NewTrigger on Child__c (after update) { if(Trigger.isAfter && Trigger.isUpdate) { NewClass.NewMethod(Trigger.New); } }
can anyone spare some time to explain once plz
//handler code -
public class NewClass { // class name
public static void NewMethod(List<Parent__c> newParent) { //created list using custom object parent and named it newParent
newParent = [SELECT Id, Name, Field1__c, Field2__c WHERE Id IN: newParent]; // fetching id, name and other fields where id is matching to newParent ? but with which other object they are comparing this ? are they fetching from newParent and assigning also in newParent ? plz explain this part
List<Child__c> childQry = new List<Child__c>(); // list created for child object
List<Child__c> childListToUpdate = new List<Child__c>(); //another list created for child object, did not understand why 2 list created here ?
for(Parent__c p : newParent) { // Parent object reference variable p created which will run through records saved in newParent list
childQry = [SELECT Id, Name, Parent__c, Field1__c, Field2__c FROM Child__c WHERE Field1__c =: p.Id]; // fetching records and assigning to list
for(Child__c c : childQry) { // loop running through childQry records
if(p.Id != null) { // null check
c.Field2__c = p.Field2__c; // assigning value to field2 from parent object field2
childListToUpdate.add(c); // inserting record in new list
}
}
}
update childListToUpdate; // updating the record, did not understand what is meaning of this, didn't we already insert record in previous line ?
}
}
//Trigger code
trigger NewTrigger on Child__c (after update) { if(Trigger.isAfter && Trigger.isUpdate) { NewClass.NewMethod(Trigger.New); } }
You have written a trigger on Child__c object and you need to pass the Child__c object records to the NewClass method called NewMethod instead of parent__c records.
You were doing dml operation on same object then you can use before update instead of after update.
Modify the trigger like below.
trigger NewTrigger on Child__c (before update) { if(Trigger.isBefore && Trigger.isUpdate) { NewClass.NewMethod(Trigger.New); } }Modify the class like below.
public class NewClass { // class name public static void NewMethod(List<Child__c> newchilds) {// List of child records //initialize set to store parent ids set<id> parentids = new set<id>(); for(Child__c c:newchilds ){ if(c.Parent__c!=Null){ parentids.add(c.Parent__c) } } Map<id,string> parentmapvalues = new Map<id,string>(); for(Parent__c p: [select id,Field2__c from Parent__c where id=:parentids AND Field2__c!=Null ]){ parentmapvalues.put(p.id,p.Field2__c); } for(Child__c c:newchilds ){ if(parentmapvalues.containskey(c.Parent__c)){ c.Field2__c = parentmapvalues.get(c.Parent__c); } } } }If this helps, Please mark it as best answer.
Thanks!!