Create list columns via Web Services

I have just spent a day up to my armpits in JavaScript, specifically JavaScript for creating columns on custom lists for a site configuration utility (where the team I was working in doesn't have developer level access to the farm).

The bulk of the work for creating lists and libraries was done by my predecessor but the scope for adding columns to a list was restricted to adding existing site columns. I need to be able to automatically create new list columns.

Using the UpdateList method of the Lists web service makes this quite simple. The tricky part is working out what parameters you use to create the fields (also applies to updating).

The CAML query for creating a field is of the format:

<Fields><Method ID="1"><Field [attributes]/><Field [attributes]/></Method></Fields>

There are lots of attributes to use for the node, but these are the common ones:

• Type: Corresponds to the column type in the Create Column screen (more details below)
• Name: Internal name of the field (replaced with the internalised version of the Display Name, see this post).
• Display Name: The visible name of the column
• Required: "TRUE" or "FALSE", whether or not this column must contain information (not applicable to Yes/No or Calculated columns)
• Description: The column description

Other attributes are used depending on the column type (with typical examples):

• Single line of text
  
  
  • Type="Text"
• Multiple lines of text
  
  
  • Type="Note"
  • AppendOnly="TRUE" (append changes to the field, but only if versioning on the list is enabled)
  • RestrictedMode="TRUE" (defines whether users can use normal rich text, or enhanced rich text)
  • RichText="TRUE" (rich or plain text)
  • NumLines="6" (number of lines to display to the user while editing)
• Choice
  
  
  • Type="Choice"
  • Format="Dropdown"
  • FillInChoice="FALSE"
  • Mult="FALSE" (sets multiple selection)
  • <CHOICES><CHOICE>Choice 1</CHOICE><CHOICE>Choice 2</CHOICE></CHOICES>
  • <Default>Choice 2</Default>
• Currency
  
  
  • Type="Currency"
  • Max="321" (maximum value)
  • Min="123" (minimum value)
  • Decimals="0" (number of decimal places)
  • LCID="1033/5129" (currency format, 1033 is USA, 5129 is NZ)
• Date and Time
  
  
  • Type="DateTime"
  • Format="DateOnly"
  • <Default>[today]</Default>
• Lookup
  
  
  • Type="Lookup"
  • List="Lists/[List Name]"
  • ShowField="Title"
  • Mult="FALSE"
• Yes/No
  
  
  • Type="Boolean"
  • <Default>Yes</Default>
• Person or Group
  
  
  • Type="User"
  • UserSelectionMode="0" (all people)
  • ShowField="ImnName" (Name with presence)
• Calculated
  
  
  • Type="Calculated"
  • ResultType="Text"
  • ReadOnly="TRUE"
  • <Formula>=If([ECM Status]="Draft","Work in progress","Submitted")</Formula>
  • <FieldRefs><FieldRef Name="ECM_x0020_Status"/></FieldRefs>