What is an iPhone app?

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 An iPhone app is a program that runs on our iPhone/iPod Touch. It enables us to accomplish a certain task. They could be utility apps, games, enterprise apps, entertainment apps, apps to access our bank account etc.

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How to use nsxmlparser in Iphone SDk?

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NSXMLParser is a forward only reader or an event driven parser. What it means is, an event is raised whenever the parser comes across a start of an element, value, CDATA and so on. The delegate of NSXMLParser can then implement these events to capture XML data. Some of the events are raised multiple times like the start of an element, value of an element and so on. Since NSXMLParser is known as an event driven parser, we can only read data at the present node and cannot go back. The iPhone only supports  NSXMLParser  and not  NSXMLDocument , which loads the whole XML tree in memory. Books Application To understand how to use an instance of NSXMLParser, let’s create a simple navigation based application where we will list the title of the book in the table view and upon selecting a title, display the detail information in a detail view. Click  here  to see the sample XML file, used in this application. Create a new application in XCode by selecting Navig...
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Core data for iPhone SDk

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Core Data helps you to save model objects (in the sense of the model-view-controller design pattern) to a file and get them back again. This is similar to archiving technology but Core Data offers much more than that. Amongst other things it… ·          Provides an infrastructure for managing all the changes to your model objects. This gives you automatic support for undo and redo, and for maintaining reciprocal relationships between objects. ·          Allows you to keep just a subset of your model objects in memory at any given time. This is especially important on iPhone where conserving memory is critical. ·          Uses a schema to describe the model objects. You define the principal features of your model classes—including the relationships between them—in a GUI-based editor. This provides a wealth of basic functionality “for free,” including setting of...
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What is atomic and nonatomic in iPhone SDk?

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The last two are identical; "atomic" is the default behavior (note that it is not actually a keyword; it is specified only by the absence of nonatomic ). Assuming that you are @synthesizing the method implementations, atomic vs. non-atomic changes the generated code. If you are writing your own setter/getters, atomic/nonatomic/retain/assign/copy are merely advisory. With "atomic", the synthesized setter/getter will ensure that a whole value is always returned from the getter or set by the setter, regardless of setter activity on any other thread. That is, if thread A is in the middle of the getter while thread B calls the setter, an actual viable value -- an autoreleased object, most likely -- will be returned to the caller in A. In nonatomic , no such guarantees are made. Thus, nonatomic is considerably faster than "atomic". What "atomic" does not do is make any guarantees about thread safety. If thread A is calling the getter s...
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