Interview Questions

Q:

Whats a struct?

Answer

A struct is a special C data type that encapsulates other pieces of data into a single cohesive unit. Like an object, but built into C.

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Q:

Whats the difference between a NSArray and a NSMutableArray?

Answer

A NSArray’s contents can not be modified once it’s been created whereas a NSMutableArray can be modified as needed, i.e items can be added/removed from it.

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Q:

If I call performSelector:withObject:afterDelay: – is the object retained?

Answer

Yes the object is retained. It creates a timer that calls a selector on the current threads run loop. It may not be 100% precise time-wise as it attempts to dequeue the message from the run loop and perform the selector.

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Q:

Explain the correct way to manage Outlets memory?

Answer

Create them as properties in the header that are retained. In the viewDidUnload set the outlets to nil(i.e self.outlet = nil). Finally in dealloc make sure to release the outlet.

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Q:

Where can you test Apple iPhone apps if you don’t have the device?

Answer

iOS Simulator can be used to test mobile applications. Xcode tool that comes along with iOS SDK includes Xcode IDE as well as the iOS Simulator. Xcode also includes all required tools and frameworks for building iOS apps.  However, it is strongly recommended to test the app on the real device before publishing it.

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Q:

Assume that your app is running in the foreground but is currently not receiving events. In which sate it would be in?

Answer

An app will be in InActive state if it is running in the foreground but is currently not receiving events. An app stays in InActive state only briefly as it transitions to a different state.

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Q:

What are layer objects and what do they represent?

Answer

Layer objects are data objects which represent visual content. Layer objects are used by views to render their content. Custom layer objects can also be added to the interface to implement complex animations and other types of sophisticated visual effects.

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Q:

What is SVG?

Answer

SVG stands for scalable vector graphics. It’s a text based graphic language which draws images using text, lines, dots etc. This makes it lightweight and renders faster.

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