Overview

A list is a set of possible values for a field or enterable object. You can use a list to:

• Provide the user choices from which to select an entry for a field or enterable object,
• Restrict the valid entries to those in the list,
• Exclude the entries in the list from being entered.

You can also create hierarchical lists. A hierarchical list associates a sublist with each item of the list.

4D lets you associate a small icon with each item in a list or hierarchical list. Where appropriate, the small icon is displayed to the left of the item. For example, you can display the small icons for scrollable areas (see DELETE INDEX), for Tab Controls and for hierarchical lists (see Hierarchical Pop-up Menus and Hierarchical Lists).

When a list is used as a choice list for a field or enterable object, the user can simply select from the list instead of typing the entry. For example, you may want to create a choice list for entering job titles in a personnel database.

You can also use lists to provide restrictions on data entry. One list may provide the required values for a field, excluding all others. Another list may provide the excluded values for a field, preventing any value in the list from being entered.

Your lists can offer up to 8,000 choices in a single database and the maximum length of each item is 2 billion characters.

For information about adding a choice list to a field as a field attribute, see the “Allow choice list” section in UNREGISTER CLIENT. For information about using lists with data entry controls, see Data entry controls and assistance. 

Lists are often used in methods. For example, a list is a convenient place to store the elements of an array. An array stores a list of values in memory. You can use lists to store the elements of pop-up menus, hierarchical lists, combo boxes, tab controls, and other multi-valued interface objects. You transfer the contents of the list to the interface object using a method or by assigning the list to the object in the Property List window.

You create 4D lists with the Lists editor found in the tool box.

Note for 4D Server: Object locking occurs when two or more users attempt to modify the same list at the same time. If a user is modifying a list in the Design environment, the list is locked. Other users cannot modify the list, the list name, or any of the items in the list, until the first user frees the list by closing it.