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Foundation Framework Reference NSUniqueIDSpecifier Class Reference

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NSUniqueIDSpecifier

Specifies an object in a collection (or container) by unique ID. This specifier works only for objects that have an ID property. The unique ID object passed to an instance of NSUniqueIDSpecifier must be either an NSNumber object or an NSString object. The exact type should match the scripting dictionary declaration of the ID attribute for the relevant scripting class.

You can expect that the ID property will be read only for any object that supports it. Therefore a scripter can obtain the unique ID for an object and refer to the object by the ID, but cannot set the unique ID.

You don’t normally subclass NSUniqueIDSpecifier.

The evaluation of NSUniqueIDSpecifier objects follows these steps until the specified object is found:

  1. If the container implements a method whose selector matches the relevant valueIn<Key>WithUniqueID: pattern established by scripting key-value coding, the method is invoked. This method can potentially be very fast, and it may be relatively easy to implement.

  2. As is the case when evaluating any script object specifier, the container of the specified object is given a chance to evaluate the object specifier. If the container class implements the indicesOfObjectsByEvaluatingObjectSpecifier: method, the method is invoked. This method can potentially be very fast, but it is relatively difficult to implement.

  3. An NSWhoseSpecifier object that specifies the first object whose relevant 'ID ' attribute matches the ID is synthesized and evaluated. The NSWhoseSpecifier object must search through all of the keyed elements in the container, looking for a match. The search is potentially very slow.

Inheritance


Conforms To


Import Statement


Swift

import Foundation

Objective-C

@import Foundation;

Availability


Available in OS X v10.2 and later.
  • Sets the ID encapsulated by the receiver.

    Declaration

    Swift

    @NSCopying var uniqueID: AnyObject

    Objective-C

    @property(copy) id uniqueID

    Parameters

    uniqueID

    The ID for the receiver.

    uniqueID must be an instance of NSNumber or NSString. The type should match the declared type of the attribute of the specified scriptable class whose four-character code is 'ID '.

    Discussion

    Although NSUniqueIDSpecifier supports setting the unique ID, the ID for a specified object is likely to remain static over the life of the object.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in OS X v10.2 and later.

    See Also

    – uniqueID

  • Returns the ID encapsulated by the receiver.

    Declaration

    Swift

    @NSCopying var uniqueID: AnyObject

    Objective-C

    @property(copy) id uniqueID

    Return Value

    The ID encapsulated by the receiver.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in OS X v10.2 and later.