Book Image

Core Data iOS Essentials

By : Bintu Harwani, B. M. Harwani
Book Image

Core Data iOS Essentials

By: Bintu Harwani, B. M. Harwani

Overview of this book

Core Data is the essential ingredient in data driven iOS apps. It's used for storing, retrieving, and manipulating application data in databases, XML, and binary formats. It's an essential component for iPhone, iPod Touch, and iPad apps.Core Data Essentials provides a clear, readable guide to the most useful aspects of Core Data. Built around a realistic example app, the book showcases the most important aspects of Core Data development in the context of a complete, functioning app written in Objective C.The book starts with a tour of how the app works. Then you'll see how to easily display data using the Table View. You'll learn how to develop an appropriate data model that fits the needs of your app, then implement that model as updatable data objects. You'll see how to update data and build relationships between objects and learn how Core Data can work with search, and how to provide your users with friendly data editing features.
Table of Contents (19 chapters)
Core Data iOS Essentials
About the Author
About the Reviewers

Understanding NSPredicate

NSPredicate is a complex and powerful tool used to filter out the undesired instances of an entity and to display only the desired instances. We can use it to construct a SQL-like query for retrieving the desired information.

We can build NSPredicate that accepts SQL-like NSString. It can accept any number of parameters after the NSString. We can see in the preceding textDidChange method that we have passed the text (entered in the text field of the Search Bar control) as an argument after the NSString. There are two useful methods of NSPredicate; let's have a look at them:

  • predicateWithFormat: This method creates a new predicate from a formatted string. The following is the syntax for it:

    +(NSPredicate *) predicateWithFormatLNSString *) formatted string, argument list;
  • evaluateWithObject: This method checks or evaluates a predicate with an object and returns a Boolean value YES - if the object matches with the Predicate (condition) - otherwise it returns a...