Find required values for salesforce objects

Question

I want to know how to find Required Fields For An Object. Either through code or through a GUI.

If I try to create a new User, I can't because some fields are required to be defined. How can I tell which one of those are required?

Answer 1

Option 1: Found this code which returns a list of all columns and which ones are nillable and createable.

@isTest
public with sharing class Test_Foobar {
  static testMethod void testFoobar(){

    Schema.DescribeSObjectResult r = User.sObjectType.getDescribe();
    Map<String,Schema.SObjectField> M = r.fields.getMap();
    for(String fieldName : M.keySet())
    { 
         Schema.SObjectField field = M.get(fieldName);
         Schema.DescribeFieldResult F = field.getDescribe();
         Boolean isFieldreq  = F.isNillable() ;

         System.debug ('F = ' + fieldName + ' isnillable = ' +  isFieldreq);
         Utils.log('F = ' + fieldName + ' isnillable = ' +  isFieldreq);
    }
  }
}

Prints a mountain of output, which I've condensed here:

F = street isnillable = true
F = street isCreateable = true
F = userpreferencesdisablebookmarkemail isnillable = false
F = userpreferencesdisablebookmarkemail isCreateable = true
...
F = fullphotourl isnillable = true
F = fullphotourl isCreateable = false

Which fields are required?

If a field is nillable then it can have no value. If a field is not nillable, it must have a value. If a field is createable then you can define it, otherwise you can't define it.

So required fields you have to define are creatable and not nillable. Bazinga.

Option 2: Attempt the insert with one field, read the Required fields are missing message:

Inside of a method, do this:

User testUser = new User(firstname = 'joe', lastname = 'bieber');
insert testUser;

You'll get an error message:

15:26:29.082 (3082662769)|VF_PAGE_MESSAGE|Required fields are missing: [Username, 
Email, Alias, CommunityNickname, TimeZoneSidKey, LocaleSidKey, EmailEncodingKey, 
ProfileId, LanguageLocaleKey]