1) What is NSArray?
NSArray is Objective-C's general-purpose array type. It represents an ordered collection of objects, and it provides a high-level interface for sorting and otherwise manipulating lists of data.

 

2) What is NSMutableArray?
NSMutableArray (and all other classes with Mutable in the name) can be modified. So, if you create a plain NSArray , you cannot change its contents later (without recreating it).

 

3) What is NSDictionary?
NSDictionary - derived from the word called entry. Each entry consists of one object that represents the key and a second object that is that key's value. Within a dictionary, the keys are unique.

 

4) What is JSON?
JSON (JavaScript Object Notation) is a lightweight data-interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. Text can be read and used as a data format by any programming language.

 

5) What is JSON Serialization?
JSON is a format that encodes objects in a string. Serialization means to convert an object

into that string, and deserialization is its inverse operation. When transmitting data or

storing them in a file, the data are required to be byte strings, but complex objects are

seldom in this format.Without using JSON

<7b226964 223a2275 35383738 37373334 31222c22 636f6d6d 616e6422 3a224745

545f5553 45525f49 4e464f22 2c227661 6c756522 3a22227d>

 

6) What does the NS prefix mean?
Next Step

 

7) What is Instance Method?
An instance method is a method that's only available on a particular instance of a class,

only after said instance of the class has already been created. A class method is a method

that can be called on the class itself, no instance necessary. For example:

YourClass *object = [[YourClass alloc] init];

[object someInstanceMethod];

 

8) How to convert an int to an NSString?
int theinteger = 10;

NSString *string = [NSString stringWithFormat:@"%d", theinteger];

 

9) How to convert String to Int
NSString *theinteger = @”10”;

int a = [theinteger intValue];

 

10) iOS UIViewController lifecycle
ViewDidLoad:
Called when you create the class and load from xib. Great for initial setup and one-time only

work.

ViewWillAppear:
Called right before your view appears, good for hiding/showing fields or any operations

that you want to happen every time before the view is visible. Because you might be

going back and forth between views, this will be called every time your view is about to

appear on the screen.

ViewDidAppear :
Called after the view appears - great place to start an animations or the loading of

external data from an API.

ViewWillDisappear/DidDisappear :
Same idea as ViewWillAppear/ViewDidAppear.

ViewDidUnload/ViewDidDispose:

In Objective C, this is where you do your clean-up and release of stuff, but this is

handled automatically so not much you really need to do here.

11) What is Delegate?
A delegate allows one object to send messages to another object when an event happens

Eg: NSURLConnection class. NSURLConnection has three common delegates:

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error

- (void)connectionDidFinishLoading:(NSURLConnection *)connection

- (void)connection:(NSURLConnection *)connection

didReceiveResponse:(NSURLResponse *)response

NSString *theinteger = @”10”;

int a = [theinteger intValue];