2.1.3 Properties list

2.1.3 Properties list

The Properties list shows the defined properties of the object type. For each property the following is shown: the Local name of the property, the type name of the property (Property Name), the Data type of the property and whether the property has unique values (Unique?) within this object type.

The local name of the property is the name that is used for the property within this object type, whereas the property name shows the name of the property type which is used everywhere in the system and shown for example in property sharing dialogs. The data type shows the type of the contents of the property (see Section 2.6.3 for details of data types): it cannot be edited directly from here.

Figure 2–2. Properties list pop-up menu.

The Properties list has a context sensitive pop-up menu (as in Figure 2–2) that is used for defining the properties and also for creating the property dialogs for this object type (see Section 2.6 for the definition of properties and Chapter 4 for the definition of property dialogs). The Properties list pop-up menu contains the following items — note that depending on various factors not all of them may be available at any given time:

	Set as Identifier sets the currently selected property to be the identifier of the object type. The identifier is the property that is shown in all selection dialogs, and which is often unique among the instances of the object type. The choice of identifier can be modified later, but notice that this will have a very visible effect, as the name of the object type’s instances that the user sees will change in many MetaEdit+ tools. The identifying property type is marked in the property list with an asterisk (*) before the local name.
	The Toggle Uniqueness menu item toggles whether values of this property type are unique within this object type. The Unique? field has a value of true or false in it according to this toggle. The default setting for uniqueness is false, and thus normally there can be many objects with the same value in their property fields (unless the property is shared). If this menu item is selected, then the values of this property must be unique within this property type, excepting e.g. empty string fields.
	The Local Name... menu item opens a dialog where the local name for the selected property can be given. Usually this can be left the same as the name of the property type, as defined in the Property Tool. If you have used general property names to maximize the possibilities for reuse and want to specialize them here, you can set a different local name here. Users in general see the local name, e.g. in property dialogs. Property sharing uses the type name, as that is the same in all non-properties.

For example you might have a property type called ‘Name’, which you want to use for all object types to allow property sharing between them. You could then use the property in object type ‘State’ in WatchApplication diagrams, giving it the internal name ‘State name’. This would allow you to reuse existing property names anywhere where the ‘Name’ property was used, but still see the familiar ‘State name’ in ‘State’ dialogs.

	The Property Definition menu item, or alternatively a double click, opens a Property Tool for the selected property (see Section 2.6 for details on using the Property Tool). The attributes of a property type can be changed in the Property Tool, affecting all types that use that property type.
	The Add Property... menu item opens a dialog containing a list of all the defined property types. Thus if you want to add an existing property type, just select its name from the list and it will be added to the properties of this object type. If you want to define a new property type, select ‘New Property Type’ from the start of the dialog list. This opens a Property Tool where the new property type can be defined. When you generate that new Property type, it will be automatically added to this Object type.
	The Change Property... menu item opens a dialog containing a list of all property types which have the same data type as the selected one. Thus if you want to change an existing property type, just select it from the properties list, choose Change Property... from the menu, and select the property type with which you want to substitute it.

If a property has been added to the Properties list but not yet saved (by pressing the Save button), it can be changed to use a property type of any data type.

Move Property... allows you to move the selected property to a different position in the list, altering the order in the default dialog for this object type. Note that inherited property types ¾ shown with dark red text ¾ must be moved in the ancestor, and this change will affect all other descendants. If you want to change the order in only one descendant, you will have to edit the dialog for that type and move the property name and widget manually there.

Remove Property removes the selected property type from this object type. Please note that inherited property types must be deleted in the ancestor, and this change will affect all other descendants. Once the change has been made, this action can only be undone by closing the Object Tool without saving, or after saving by abandoning the transaction; adding the same property type back with the same name will create a new property field, the value of which will be empty in all instances.