How to show results in a list Grails gsp

Question

I have the Student class that has a relationship one-to-many with the Note class

class Student {
   String name
   static hasMany = [notes: Note]
}

class Note {
    double note
    int bimester
    static belongsTo = [student:Student]
}

When I display the result to the user in my userNotes.gsp It is shown: I use: <g:each var="n" in="${studentInstance.notes}">

Discipline    Note  Bimester
mathematics | 0    |   1
mathematics | 0    |   2
mathematics | 0    |   3
mathematics | 0    |   4
portuguese  | 0    |   1
portuguese  | 0    |   2
portuguese  | 0    |   3
portuguese  | 0    |   4

But I wanted to show the following:

Discipline | Bimester 1 | Bimester 2 | Bimester 3 | Bimester 4
mathematics      0            0            0            0
portuguese       0            0            0            0

Answer 1

You can group the data in the controller:

def userNotes() {
   def student = Student.get(1)
   def disciplines = [:].withDefault { [0, 0, 0, 0] }
   for (Note note in student.notes.sort { it.bimester }) {
       disciplines[note.discipline].set(note.bimester - 1, note.note)
   }
   [disciplines: disciplines]
}

and display it with

<table>
    <thead>
        <tr>
            <th>Discipline</th>
            <th>Bimester 1</th>
            <th>Bimester 2</th>
            <th>Bimester 3</th>
            <th>Bimester 4</th>
        </tr>
    </thead>
    <tbody>
    <g:each in="${disciplines}" var="entry">
        <tr>
            <td>${entry.key}</td>
            <g:each in="${entry.value}" var='bimester'>
            <td>${bimester}</td>
            </g:each>
        </tr>
    </g:each>
    </tbody>
</table>