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iOS Swift 2.0 Collections and Control Flow Dictionaries Dealing With Non-Existent Data

Raphael Reiter
Raphael Reiter
6,820 Points
Posted by Raphael Reiter
Raphael Reiter
6,820 Points

Arrays Vs Dictionaries

Hi

It seems like the syntax for arrays and dictionaries are the same. How do we differentiate the two?

Best

R

1 Answer

Steve Hunter
Steve Hunter
57,712 Points
Steve Hunter
Steve Hunter
57,712 Points

Hi Raphael,

The key difference between an array and a dictionary is order. An array will preserve the order of its elements - a dictionary does not need to.

An array is a store of objects in a row with an index referring to each elements' position - [0], [1], [2] etc. Whatever you store at [1] will remain at [1] and that will always be 'after' [0] and 'before' [2]. You can access the first, last, next and previous elements in an array with consistent results - their order is preserved.

A dictionary stores key/value pairs. Each key is unique and is used to access the corresponding value - where those key/value pairs are in relation to each other is both irrelevant an uncontrolled - don't try to access the 'next' element of a dictionary as you could get anything returned. There are plenty of dictionary examples in the preceding videos - it doesn't need me to make one up to illustrate the point!

I hope that helps.

Steve.