Accessor Search Implementation Details

Accessor Search Patterns for Simple Attributes

Accessor Search Pattern for Ordered Collections

The default search pattern for mutableArrayValueForKey: is as follows:

1. The receiver's class is searched for a pair of methods whose names match the patterns insertObject:in<Key>AtIndex: and removeObjectFrom<Key>AtIndex: (corresponding to the NSMutableArray primitive methods insertObject:atIndex: and removeObjectAtIndex: respectively), or methods matching the pattern insert<Key>:atIndexes: and remove<Key>AtIndexes: (corresponding to the NSMutableArrayinsertObjects:atIndexes: and removeObjectsAtIndexes: methods).

   If at least one insertion method and at least one removal method are found each NSMutableArray message sent to the collection proxy object will result in some combination of insertObject:in<Key>AtIndex:, removeObjectFrom<Key>AtIndex:, insert<Key>:atIndexes:, and remove<Key>AtIndexes: messages being sent to the original receiver of mutableArrayValueForKey:.

   If receiver's class also implements the optional replace object method matching the pattern replaceObjectIn<Key>AtIndex:withObject: or replace<Key>AtIndexes:with<Key>: that method will be used when appropriate for best performance.

2. Otherwise, the receiver's class is searched for an accessor method whose name matches the pattern set<Key>:. If such a method is found each NSMutableArray message sent to the collection proxy object will result in a set<Key>: message being sent to the original receiver of mutableArrayValueForKey:. It is much more efficient to implement the indexed accessor methods discussed in the previous step.

3. Otherwise, if the receiver's class responds YES to accessInstanceVariablesDirectly, the receiver's class is searched for an instance variable whose name matches the pattern _<key> or <key>, in that order.

   If such an instance variable is found, each NSMutableArray message sent to the collection proxy object will be forwarded to the instance variable's value, which typically will be an instance of NSMutableArray or a subclass of NSMutableArray.

4. Otherwise, returns a mutable collection proxy object that results in a setValue:forUndefinedKey: message being sent to the original receiver of the mutableArrayValueForKey: message whenever the proxy receives an NSMutableArray message.

   The default implementation of setValue:forUndefinedKey: raises an NSUndefinedKeyException, but you can override it in your application.

Accessor Search Pattern for Uniquing Ordered Collections

The default implementation of mutableOrderedSetValueForKey: recognizes the same simple accessor methods and ordered set accessor methods as valueForKey (see “Default Search Pattern for valueForKey:”), and follows the same direct instance variable access policies, but always returns a mutable collection proxy object instead of the immutable collection that valueForKey: would return. It also:

1. Searches the class of the receiver for methods whose names match the patterns insertObject:in<Key>AtIndex: and removeObjectFrom<Key>AtIndex: (corresponding to the two most primitive methods defined by the NSMutableOrderedSet class), and also insert<Key>:atIndexes: and remove<Key>AtIndexes: (corresponding to insertObjects:atIndexes:] and removeObjectsAtIndexes:).

   If at least one insertion method and at least one removal method are found each NSMutableOrderedSet message sent to the collection proxy object will result in some combination of insertObject:in<Key>AtIndex:, removeObjectFrom<Key>AtIndex:, insert<Key>:atIndexes:, and remove<Key>AtIndexes: messages being sent to the original receiver of mutableOrderedSetValueForKey:.

   If the class of the receiver also implements an optional method whose name matches the pattern replaceObjectIn<Key>AtIndex:withObject: or replace<Key>AtIndexes:with<Key>: that method will be used when appropriate for best performance.

2. Otherwise, searches the class of the receiver for an accessor method whose name matches the pattern set<Key>:. If such a method is found each NSMutableOrderedSet message sent to the collection proxy object will result in a set<Key>: message being sent to the original receiver of mutableOrderedSetValueForKey:.

3. Otherwise, if the receiver’s class’s accessInstanceVariablesDirectly method returns YES, searches the class of the receiver for an instance variable whose name matches the pattern _<key> or <key>, in that order. If such an instance variable is found, each NSMutableOrderedSet message sent to the collection proxy object will be forwarded to the instance variable’s value, which therefore must typically be an instance of NSMutableOrderedSet or of a subclass of NSMutableOrderedSet.

4. Otherwise, returns a mutable collection proxy object anyway. Each NSMutableOrderedSet message sent to the collection proxy object will result in a setValue:forUndefinedKey: message being sent to the original receiver of mutableOrderedSetValueForKey:. The default implementation of setValue:forUndefinedKey: raises an NSUndefinedKeyException, but you can override it in your application.

Accessor Search Pattern for Unordered Collections

The default search pattern for mutableSetValueForKey: is as follows:

1. Searches the receiver's class for methods whose names match the patterns add<Key>Object: and remove<Key>Object: (corresponding to the NSMutableSet primitive methods addObject: and removeObject: respectively) and also add<Key>: and remove<Key>: (corresponding to NSMutableSet methods unionSet: and minusSet:). If at least one addition method and at least one removal method are found each NSMutableSet message sent to the collection proxy object will result in some combination of add<Key>Object:, remove<Key>Object:, add<Key>:, and remove<Key>: messages being sent to the original receiver of mutableSetValueForKey:.

   If the class of the receiver also implements an optional method whose name matches the pattern intersect<Key>: or set<Key>:, that method will be used when appropriate for best performance.

2. If the receiver is a managed object, the search pattern does not continue as it would for non-managed objects. See “Managed Object Accessor Methods” in Core Data Programming Guide for more information.

3. Otherwise, the receiver's class is searched for an accessor method whose name matches the pattern set<Key>:. If such a method is found, each NSMutableSet message sent to the collection proxy object will result in a set<Key>: message being sent to the original receiver of mutableSetValueForKey:.

4. Otherwise, if the receiver's class method accessInstanceVariablesDirectly returns YES, the class is searched for an instance variable whose name matches the pattern _<key> or <key>, in that order. If such an instance variable is found, each NSMutableSet message sent to the collection proxy object will be forwarded to the instance variable's value, which therefore must typically be an instance of NSMutableSet or a subclass of NSMutableSet.

5. Otherwise, returns a mutable collection proxy object anyway. Each NSMutableSet message sent to the collection proxy object will result in a setValue:forUndefinedKey: message being sent to the original receiver of mutableSetValueForKey:.