How to sort wrapper which has custom sobject

Question

I want to sort a custom wrapper list. A piece of code is shown below.

public List<Subscription__c> subs;  
public TerritoryBusinessUnit__c tlBU;

public class wrap {

        public boolean selection { set; get; }
        public subscription__c sub { set; get; }

        public wrap(boolean sel, subscription__c s) {

            selection = sel;
            sub = s;
        }
    }

public List<wrap> wrapls = new List<wrap>();

    public List<wrap> subList { 
        set; 
        get{
            return wrapls;
        } 
    }

public void Laodsubscriptions()
{
  subs=[some condition here]

tlBU=[SELECT ID,Name, TerritoryLabel__c, MID__c, FetchType__c,Address__c
                    FROM TerritoryBusinessUnit__c
                    WHERE MID__c=:ApexPages.currentpage().getparameters().get('mid')];

if(tlBu.FetchType__c == 'L')
{
  //some logic
}

wraps.sort();
}

Error:

One or more of the items in this list is not Comparable.

Please let me know what best can be done to resolve this.

Answer 1

This interface is covered in the Apex Developer Guide:

Comparable Interface

Adds sorting support for Lists that contain non-primitive types, that is, Lists of user-defined types.

global class Employee implements Comparable {

    public Long id;
    public String name;
    public String phone;
    
    // Constructor
    public Employee(Long i, String n, String p) {
        id = i;
        name = n;
        phone = p;
    }
    
    // Implement the compareTo() method
    global Integer compareTo(Object compareTo) {
        Employee compareToEmp = (Employee)compareTo;
        if (id == compareToEmp.id) return 0;
        if (id > compareToEmp.id) return 1;
        return -1;        
    }
}

Please, never use the global access modifier unless you know of a solid reason you need it. Replace global with public when rolling your own implementation.