How can i resolve Constructor not defined error?

Question

I have created class using custom setting. I need to retrieve data from custom setting. I am getting constructor not defined error my error line is options.add(new SelectOption)Please find below code. How can I resolve this error. Please can any one suggest me.

Controller:

public with sharing class CustomSettingsController {

    public string ISOCode {get;set;}
    public list<RFLEET_CS01_Grid_Protocol_Lines__c> options_list {get;set;}
    public list<RFLEET_CS01_Grid_Protocol_Lines__c> options_list_Split {get;set;}

     public String selectedIso {get;set;}

     public List<selectOption> isoCodes {
        get {
          List<selectOption> options = new List<selectOption>();

            for (RFLEET_CS01_Grid_Protocol_Lines__c iso : RFLEET_CS01_Grid_Protocol_Lines__c.getAll().values())

            options.add(new SelectOption(iso.Model__c,iso.Name+' - '+iso.Model__c));
            return options;

        }
        set;
      }

     public void getrecords(){

           options_list = new list<RFLEET_CS01_Grid_Protocol_Lines__c>();
           options_list= [SELECT Name,Model__c FROM RFLEET_CS01_Grid_Protocol_Lines__c WHERE Model__c = :ISOCode];


      }
       public void SplitRecords(){

           options_list_Split = new list<RFLEET_CS01_Grid_Protocol_Lines__c>();

          //for (Country_Custom_Setting__c iso : Country_Custom_Setting__c.getAll().values())
           // options.add(new SelectOption(iso.Model__c,iso.Name));
             options_list_Split= [SELECT Name,Model__c FROM RFLEET_CS01_Grid_Protocol_Lines__c WHERE Model__c = :ISOCode];
             //return null;

      }


}

Answer 1

The SelectOption constructors signature is

public SelectOption(String value, String label)

Your error may be caused by the Model__c field, if it is not a String then you will get error you are seeing.

You could convert it to a String in the following way:

String.valueOf(iso.Model__c)

Be aware that if Model__c is null then the above line will result in the String 'null'