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Introduction to Key-Value Coding Programming Guide

Contents:

Organization of This Document
See Also

Key-value coding provides a mechanism for accessing an object’s properties indirectly.

The techniques for using key-value coding differ slightly between Objective-C and Java. Key-value coding in Objective-C is largely managed by the NSKeyValueCoding informal protocol, which is implemented by the NSObject class. Only two methods from this protocol are available in Java. Instead, in Java most key-value coding is implemented in the NSKeyValue class.

You should read this document to gain an understanding of how to use key-value coding in your applications. Key-value coding is a key technology when working with Cocoa bindings and Core Data. You are expected to be familiar with the basics of Cocoa development, including the Objective-C language and memory management.

Organization of This Document

Key-Value Coding includes these articles:

• “What is Key-Value Coding?” provides an overview of key-value coding.

• “Terminology” defines the terms commonly used to refer to an object’s properties.

• “Key-Value Coding Fundamentals” describes the basic principles required to use key-value coding.

• “Key-Value Coding Accessor Methods” describes the accessor methods your classes should implement.

• “Key-Value Validation” tells you how to implement property validation.

• “Ensuring KVC Compliance” describes the capabilities a class must implement to be key-value coding compliant.

• “Scalar and Structure Support” describes the data types supported by key-value coding.

• “Set and Array Operators” lists the available collection operators and describes their use.

• “Accessor Search Implementation Details” explains how the appropriate accessor method or instance variable is determined.

• “Describing Property Relationships” describes the use of meta-data to define the relationships between objects and their properties.

• “Performance Considerations” describes the performance considerations when using key-value coding.

See Also

There are other technologies, not covered in this document, that are related to key-value coding.

• Key-Value Observing Programming Guide describes the features of the key-value observing protocol that allows objects to observe changes in other objects.

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