Introduction to the Swift Language - Chicago Swift Developer Meetup - Screen 6 on FlowVella - Presentation Software for Mac iPad and iPhone

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Optional variables must be unwrapped using ! to access their value

Swift: Trying hard to help you avoid doing something dumb and getting NPEs

// Optional integer,

// allowed to be nil

var myOptionalVar : Int? = nil

myOptionalVar = 100

println (myOptionalVar! + 1)

Required Values

Variables in Swift are required to

have values (usually, see below)

Optional Variables

Optional variables are explicitly declared that they may have the value of nil

See this article for a lot more detail on optionals:

https://medium.com/swift-programming/facets-of-swift-part-1-optionals-b8ba5b0051a2

Use ! to Unwrap Optional Variables

Note the use of the exclamation point (!) at the end of the variable name in the last line

Tony Hoare, the inventor of null, considers his own invention a “billion dollar mistake”

Null References: The Billion Dollar Mistake, Tony Hoare, 2009

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Introduction to the Swift Language - Chicago Swift Developer Meetup

v 2015-04-13a

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