How to sort a custom list of Notes and Attachments by LastModifiedDate

Question

In my VF Page I have been asked to show a list of all the Notes and Attachments in one table, and sorted by the common LastModifiedDate ...

So I have a wrapper class in my custom controller:

public List<wNA> rowList {get; set;}  

public class wNA{

    public string Type {get; set;}
    public string Id {get; set;}
    public string fileName {get; set;}
    public string createdBy {get; set;}
    public datetime LastModifiedDate {get; set;}
    public string contentType {get; set;}
}

and in the constructor:

rowList = new List <wNA>();
wNA tr = new Wna();

system.debug('RFSCController CONSTRUCTOR get Attachments into List with Parent:' + recordid);

List<Attachment> lstAttachments= new List<Attachment>(); {
    lstAttachments = [SELECT Id, Name, LastModifiedDate, contentType, OwnerId from Attachment where ParentId =:recordid];
}

system.debug('RFSCController CONSTRUCTOR Attachments Count:' + lstAttachments.size());

if (lstAttachments.size()!=0){
    for (Integer iDx=0; iDx<lstAttachments.size(); iDx++){

        tr.Type = 'Attachment';
        tr.Id = lstAttachments[iDx].Id;
        tr.fileName = lstAttachments[iDx].Name;
        tr.createdBy = lstAttachments[iDx].OwnerId;
        tr.contentType = lstAttachments[iDx].contentType;
        tr.LastModifiedDate = lstAttachments[iDx].LastModifiedDate;

        rowList.add(tr);
    }       // Attachment att:[SELECT Id, Name, LastModifiedDate, contentType, OwnerId from Attachment where ParentId =:recordid]   
}

system.debug('RFSCController CONSTRUCTOR get Notes into List with Parent:' + recordid);

List<Note> lstNotes= new List<Note>(); {
    lstNotes = [SELECT Id, Title, ParentId, LastModifiedDate, createdbyid, body FROM Note where ParentId =:recordid];
}

if (lstNotes.size()!=0){
    for (Integer iDx=0; idx<lstNotes.size(); idx++){
        tr.Type = 'Note';
        tr.Id = lstNotes[iDx].Id;
        tr.fileName = lstNotes[iDx].Title;
        tr.createdBy = lstNotes[iDx].createdbyid;
        tr.LastModifiedDate = lstNotes[iDx].LastModifiedDate;           

        rowList.add(tr);       
    }           

}

in my previous question I was advised by crmprogdev to look at casting to a common object and comparable types

I can see in the docs here how to sort by a common field, but I cannot work out how to cast different objects to a common type...

I tried following the article on Custom Sort Order of Objects and came up with the below changes, but I am now stuck as really I need to cast the Notes and Attachments to a common type, then sort it...

public class wNA implements Comparable {

    public Note nt;
    public Attachment att;

    public wNA(Note myNote, Attachment myAtt){
        nt=myNote;
        att=myAtt;
    }

    public datetime compareToObj(Object compareTo){
        wNA compareTont = (wNA).compareTo;

        //datetime returnValue=Now();

        if (nt.LastModifiedDate>compareToObj.att.LastModifiedDate){ 
            return nt;}
        else if (nt.LastModifiedDate<>compareToObj.att.LastModifiedDate){
            return att;
        }

    }
    public string Type {get; set;}
    public string Id {get; set;}
    public string fileName {get; set;}
    public string createdBy {get; set;}
    public datetime LastModifiedDate {get; set;}
    public string contentType {get; set;}

    //Notes=[SELECT Id, Title, CreatedDate, createdbyid, body FROM Notes]

    //Attachments=[SELECT Id, Name, ContentType, OwnerId, CreatedDate  FROM Attachments];
}        

Can anyone help me get started?

What common type should I cast these attachments and Notes to?

And how do I then rebuild my list in order of the LastModifieddate field?

Answer 1

You need to implement the Comparable interface:

public class wNA implements Comparable {
    // The rest of this code remains the same; add the following function:
    public Integer compareTo(Object o) {
    return (LastModifiedDate.getTime()-((wNA)o).LastModifiedDate.getTime()).intValue();
    }
}

At this point, you can then sort your list after adding all the records to the common wrapper:

rowList.sort();

---

rowList = new List <wNA>();

List<Attachment> lstAttachments= [SELECT Id, Name, LastModifiedDate, contentType, OwnerId from Attachment where ParentId =:recordid];

    for (Integer iDx=0; iDx<lstAttachments.size(); iDx++){
        wNA tr = new wNA();
        tr.Type = 'Attachment';
        tr.Id = lstAttachments[iDx].Id;
        tr.fileName = lstAttachments[iDx].Name;
        tr.createdBy = lstAttachments[iDx].OwnerId;
        tr.contentType = lstAttachments[iDx].contentType;
        tr.LastModifiedDate = lstAttachments[iDx].LastModifiedDate;

        rowList.add(tr);
    }
}

List<Note> lstNotes= [SELECT Id, Title, ParentId, LastModifiedDate, createdbyid, body FROM Note where ParentId =:recordid];

    for (Integer iDx=0; idx<lstNotes.size(); idx++){
        wNA tr = new wNA();
        tr.Type = 'Note';
        tr.Id = lstNotes[iDx].Id;
        tr.fileName = lstNotes[iDx].Title;
        tr.createdBy = lstNotes[iDx].createdbyid;
        tr.LastModifiedDate = lstNotes[iDx].LastModifiedDate;           
        rowList.add(tr);
    }           
    rowList.sort();
}