[SalesForce] how do i create trigger on attachment

Here is my POC to show that winter '14 don't have such issue like On inserting an Attachment from UI doesn't fire the trigger.

I create the trigger and Apex class from the sample you provided and then inserted an Test Attachment file from UI on a record.

Trigger:

Class:

Debug: Debug logs created for attachment trigger and System.debug lines were there.

Attachment has been renamed as "test"

However on attachment upload notification detail page it doesn't show the name changed (even trigger got fired). It shows changed name (as sample trigger did) in related list.

There were no issues in trigger, may be this issue has been solved. Hope this help.

In before Insert Trigger, you do not have ID and that record doesn't exists in the database, thus your querry [SELECT id,Name,ParentId,Parent.Name FROM Attachment WHERE ParentId IN:objParentIds] will fail.

The logic here is to let the insert happen, and in after insert trigger do a DML to update the name of attachment with that of parent's Name. Thus your logic or trigger should be after insert.

trigger renameAttachment on Attachment (after insert) {
    List<Attachment> toBeUpdatedAttachment = new List<Attachment>();
    for(Attachment objAttachment : [SELECT id,Name,ParentId,Parent.Name FROM Attachment WHERE Id IN:Trigger.new]){
                   objAttachment.Name = objAttachment.Parent.Name;
                   toBeUpdatedAttachment.add(objAttachment);

    }

      update toBeUpdatedAttachment;
 }