iOS Interview Questions And Answers Part 25

1.What is the use of store kit framework?
​
Answer:

The Store Kit framework provides classes that allow an app to request payment from a user for additional functionality or content that your application provides.

Store Kit framework allows user to create a In-App Purchase store inside your application. 

The framework connects to the AppStore on your app’s behalf to securely process payments from users, prompting them to authorize payment.

​StoreKit manages transactions for In-App Purchases.

The framework then notifies your app, which provides the purchased items to users.
In-App Purchase used to collect payment for additional features and content.

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2.How to compare two NSDate values in Objective C ?
Answer:

Here's an example using the NSDate method, compare:
It explains an easy way to compare two dates.


NSDate *currentDate = [NSDate date];
NSDate * currentDate = [NSDate dateWithString:@”Next Date”];
NSComparisonResult  ResultDate = [currentDate compare : currentDate];
if (ResultDate == NSOrderedAscending)
{
NSLog(@”ResultDate is in the future”);
}
else if (ResultDate == NSOrderDescending)
{
NSLog(@”ResultDate is in the past”);
}
else
{
NSLog(@”Both dates are the same”);
}

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3.How to calculate number of days between two NSDates in Objective C ?
Answer:

+ (NSInteger)NumberOfDaysBetweenDate:(NSDate*)fromDateTime andDate:(NSDate*)toDateTime
{
 NSDate *fromDate;
 NSDate *toDate;
NSCalendar *calendar = [NSCalendar currentCalendar];
[calendar rangeOfUnit:NSCalendarUnitDay startDate:&fromDate interval:NULL forDate:fromDateTime];
[calendar rangeOfUnit:NSCalendarUnitDay startDate:&toDate  interval:NULL forDate:toDateTime];
 NSDateComponents *differenceResult = [calendar components:NSCalendarUnitDay
        fromDate:fromDate toDate:toDate options:0];
    return [differenceResult day];
}

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4.What is Metal in iOS?
Answer:

Apple introduced a latest API for GPU-accelerated 3D graphics in iOS 8,which is called as Metal.

Is Metal Similar to OpenGLS?
Yes,it is a low-level API that interacts with 3D graphics hardware.Metal is not cross platform but OpenGL ES is cross platform.
Metal is much more efficient with Apple hardware, providing much improved speed and low overhead compared to using OpenGL ES.

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5.What are the features of Game Kit Framework?
Answer:

Let’s point out some features of Gamekit framework:
It offers Game Center functionalities.
Game Center provides a centralized service that connects players to each other.
Users connect to Game Center and interact with other players through an alias.

Players can set status messages as well as mark other players as friends.

Multiplayer Functionality:
It allows your game to create network matches that connect players through Game Center.
Players can invite their friends or be connected to anonymous players. 
Most importantly, players can receive invitations to join a match even when your game is not running. 

​Your game is running on each device and the instances of your game exchange match and voice data with each other.

Turn-Based Gaming :
It offers store-and-forward network match infrastructure where the match is played 
out over a series of discrete turns. This kind of match can be played without requiring all of the players 
to be connected to Game Center simultaneously.

Leaderboards :
It allows your game to store and fetch player scores from Game Center.

Achievements :
It provides the ability to track a player’s accomplishments in your game.

Challenges :
It allows a player to challenge other players to complete an achievement or to beat a
 leaderboard score.

Note:        
Game Center is available on iOS and OS X.

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