The mooR Book

Property Information Functions

property_info

Description: Retrieves information about a property on an object.
Arguments:

• : The object that has the property object
• : The name of the property to get information about prop-name

Returns: A list containing two elements:

1. The owner of the property (object reference)
2. A string representing the permission flags: 'r' (read), 'w' (write), 'c' (clear)

Note: Requires read permission on the property.

property_info_hash

str|binary property_info_hash(obj object, str|sym prop-name [, str algorithm] [, int binary])

Returns a hash of the value returned by property_info(object, prop-name).

Use this to detect changes to the property's owner or permission flags separately from changes to the property's value. The optional algorithm and binary arguments work the same way as they do for value_hash().

This is a mooR extension.

set_property_info

Description: Changes the permission information for a property.
Arguments:

• : The object with the property to modify object
• : The name of the property to modify prop-name
• : A list containing permission information: [owner, permissions] or [owner, permissions, new-name]
  • : The new owner of the property (object reference) owner
  • : A string containing the permission flags (combination of 'r', 'w', 'c') permissions
  • new-name: Optional new name for the property

info

Returns: An empty list
Note: Requires appropriate permissions to modify the property.

Property Management Functions

add_property

Description: Adds a new property to an object.
Arguments:

• : The object to add the property to object
• : The name for the new property prop-name
• : The initial value for the property value
• : A list containing permission information (same format as in ) infoset_property_info``

Returns: none
Note: Requires appropriate permissions to add properties to the object.

delete_property

Description: Removes a property from an object.
Arguments:

• : The object to remove the property from object
• : The name of the property to remove prop-name

Returns: An empty list
Note: Requires ownership of the property or the object.

Property Value Functions

property_value_hash

str|binary property_value_hash(obj object, str|sym prop-name [, str algorithm] [, int binary])

Returns a hash of the resolved property value, using the same permission checks as reading the property. This is useful for detecting whether authored property state changed since some recorded base revision.

This is a mooR extension.

property_metadata_hash

str|binary property_metadata_hash(obj object, str|sym prop-name [, str algorithm] [, int binary])

Returns a hash of the map returned by property_metadata(object, prop-name).

Use this when metadata attached to the property is itself part of the state you want to compare. This is a mooR extension.

is_clear_property

Description: Checks if a property is cleared, meaning its value will be resolved transitively from a parent object through prototype inheritance.
Arguments:

• : The object to check object
• : The name of the property to check prop-name

Returns: A boolean value (true if the property is clear)
Note: Requires read permission on the property.

clear_property

Description: Clears a property, making its value be resolved transitively from a parent object through prototype inheritance.
Arguments:

• : The object with the property to clear object
• : The name of the property to clear prop-name

Returns: An empty list
Note: Requires write permission on the property.

Property Permissions Explained

Properties in this system use a permission model based on the following flags:

• (read): Controls who can read the property's value r
• w (write): Controls who can change the property's value
• (clear): Controls who can clear the property, allowing its value to be resolved from parent objects c

These permissions are represented as a string (e.g., "rwc" for all permissions, "r" for read-only).

Property Info List Format

Several functions use a property info list format:

• Two-element format: [owner, permissions]
• Three-element format: [owner, permissions, new-name]

Where:

• is an object reference owner
• is a string containing the permission flags (combination of 'r', 'w', 'c') permissions
• new-name (when present) is a string representing the new name for the property

Property Inheritance

This system uses prototype-based inheritance for properties:

• When a property is "cleared" on an object, it doesn't store its own value
• Instead, when accessing a cleared property, the system looks for that property on parent/prototype objects
• This enables efficient inheritance of property values without duplication