Update Array of nested list

Question

Hello community, 
 I have the following scenario, 
 I have a array of student details. It has fields like student id, subject id, question paper id. I want to group by subject id and update the question paper id in the array. 
 
 Given Array 1: 
 
 {student id: 100, subject id: "S1", question paper id: }, 
 {student id: 200, subject id: "S2", question paper id: }, 
 {student id: 300, subject id: "S1", question paper id: }, 
 {student id: 400, subject id: "S2", question paper id: } 
 {student id: 300, subject id: "S1", question paper id: }, 
 {student id: 300, subject id: "S3", question paper id: }, 
 
 Array 2: 
 {Q1,Q2,Q3} 
 
 Array 3 : 
 { S1,S2,S3}

Expected Output: 
 {student id: 100, subject id: "S1", question paper id: "Q1"}, 
 {student id: 200, subject id: "S2", question paper id: "Q2"}, 
 {student id: 300, subject id: "S1", question paper id: "Q1"}, 
 {student id: 400, subject id: "S2", question paper id: "Q2"} 
 {student id: 300, subject id: "S1", question paper id: "Q1"}, 
 {student id: 300, subject id: "S3", question paper id: "Q3"},

Dave Lewis · Answer

a!forEach( 
 items: array 1, 
 expression: */ if you have the cdt manipulation plugin /* 
 updateCDT( 
 fv!item, 
 "questionPaperId", 
 */ this uses the position in array 3 to find the right question in array 2 inline /* 
 index (array 2, wherecontains( array 3, fv!item.subjectId), {}) 
 ) 
 */ if you don't have the plugin, but it is a CDT */ 
 type!CDTName( 
 studentID: fv!item.studentID, 
 subjectId: fv!item.subjectId, 
 */ this uses the position in array 3 to find the right question in array 2 inline /* 
 questionPaperId: index (array 2, wherecontains( array 3, fv!item.subjectId), {}) 
 ) 
 */ if it's not a cdt but a dictionary, and if you happen to be using a rule to get the ID from the subject ID /* 
 { studentId: fv!item.studentId, subjectId: fv!item.subjectId, questionPaperId: rule!getQuestionPaperId(fv!item.subjectID) } 
 ) 
 If you are expecting the possibility of nulls, you might make it a little more robust with index() or property() functions, but dot notation here for readability, and it will work with dot notation. 
 You either run the updateCDT function, or you have each loop create a new CDT or new dictionary exactly like the old one aside from the changes. You take the brand new set and save it over the old set, i.e. in the same place, and it's LIKE you updated it.