Checking if a Method or Property Exists in an Object using Objective-C | iOS Programmer Guide

There is a simple way of testing if a method exist in an object using Objective-C. This can be achieved using the respondsToSelector method. The code snippet is given below if ([obj......

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Getting Integer Month, Day and Year from NSDate | Explain the use of NSDateComponents? | iOS Interview Question | iOS Programmer Guide

We can get day, month and year components of NSDate in integer form. For example, if the date is 1/2/2014 then we should get 1, 2 and 2014 separately as an integer. We can achieve......

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How to get UTC Date and Time Using Objective-C? | iOS Interview Question | iOS Programmer Guide

We can get UTC date & time with the help of the below objective c user defined function. -(NSString *)getUTCFormateDate:(NSDate *)localDate { NSDateFormatter *dateFormatter......

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Custom Classes in Objective-C | iOS Programmer Guide

When you're defining your own classes, you should at a minimum inherit from NSObject.If you want to define a custom button for use in an iOS app, for example, and the provided......

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Root Class Provides Base Functionality in Objective-C | iOS Programmer Guide

When an Objective-C object needs to work with an instance of another class, it is expected that the other class offers certain basic characteristics and behavior. For this reason, Objective-C defines a root class from which the vast majority of other classes inherit, called NSObject. When one object encounters another object, it expects to be able to interact using at least the basic behavior defined by the NSObject class description.

Classes Can Inherit from Other Classes in Objective-C | iOS Programmer Guide

When one class inherits from another, the child inherits all the behavior and properties defined by the parent. It also has the opportunity either to define its own additional behavior and properties, or override the behavior of the parent.

In the case of Objective-C string classes, the class description for NSMutableString specifies that the class inherits from NSString, All of the functionality provided by NSString is available in NSMutableString, such as querying specific characters or requesting new uppercase strings, but NSMutableString adds methods that allow you to append, insert, replace or delete substrings and individual characters.

What is Classes in Objective-C? | iOS Interview Question | iOS Programmer Guide

A class describes the behavior and properties common to any particular type of object. For a string object, It is an instance of the class NSString.
every instance of a class shares the same properties and behavior as all other instances of that class. Every NSString instance behaves in the same way, regardless of the internal string of characters it holds.

Some classes define objects that are immutable. This means that the internal contents must be set when an object is created, and cannot subsequently be changed by other objects. In Objective-C, all basic NSString and NSNumber objects are immutable. If you need to represent a different number, you must use a new NSNumber instance.

Some immutable classes also offer a mutable version. If you specifically need to change the contents of a string at runtime, for example by appending characters as they are received over a network connection, you can use an instance of the NSMutableString class. Instances of this class behave just like NSString objects, except that they also offer functionality to change the characters that the object represents.

Fundamentals of Objective C | iOS Programmer Guide

Objective-C is the primary programming language you use when writing software for OS X and iOS. It's a superset of the C programming language and provides object-oriented capabilities......

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Adding UIToolbar On Top of Keyboard in Objective-C | iOS Programmer Guide

We can add UIToolbar on top of the keyboard via code in iOS. First, create and instantiate an UIToolbar as given below: UIToolbar *keyboardToolbar = [[UIToolbar alloc] initWithFrame:......

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Creating Forms Using UITableView and UITextField | iOS Programmer Guide

To create a form that resembles the Gmail form in the iPhone Mail application, create a UITableView and add a UITextField into each UITableViewCell. You can download the source......

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Explain Relationship of the Frame, Bounds, and Center Properties in UIView | iOS Interview Question | iOS Programmer Guide

A view object tracks its size and location using its frame, bounds, and center properties: The frame property contains the frame rectangle,......

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Adding Section and Index List in UITableView | Indexing In UITableView | iOS Programmer Guide

Let us see how to add an index list in a UITableView. An indexed table view is more or less as the plain-styled table view. The only difference is that it includes an index on the......

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Explain UIView Drawing Cycle in iOS App? | iOS Interview Question | iOS Programmer Guide

The UIView class uses an on-demand drawing model for presenting content. When a view first appears on the screen, the system asks it to draw its content. The system captures......

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Relationship Between Superviews and Subviews in iOS | Explain View Hierarchies in iOS Application | iOS Programmer Guide

In addition to providing its own content, a view can act as a container for other views. When one view contains another, a parent-child relationship is created between the two views.......

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Explain About iOS Notification? | iOS Interview Question | iOS Programmer Guide

A notification is a message sent to one or more observing objects to inform them of an event in a program. The notification mechanism of Cocoa follows a broadcast model. It is a......

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Avoiding Adding Multiple NSNotification Observer | iOS Programmer Guide

There is no predefined way of detecting if an observer has already been added for a particular NSNotification. So the best way to avoid adding multiple NSNotification observers is......

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