A declared property effectively declares accessor methods for a property, and so conventions for naming a declared property are broadly the same as those for naming accessor methods (see Accessor Methods). If the property is expressed as a noun or a verb, the format is:
@property (…) type nounOrVerb;
If the name of a declared property is expressed as an adjective, however, the property name omits the “is” prefix but specifies the conventional name for the get accessor, for example:
@property (assign, getter=isEditable) BOOL editable;
For Apple guidelines, please refer Declared Properties and Instance Variables