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Clayton Walker 2015-10-08 23:27:19 -04:00
parent ad16a31c07
commit b4860de42f
1 changed files with 5 additions and 5 deletions
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swift.html.markdown
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@ -58,8 +58,8 @@ let piText = "Pi = \(π), Pi 2 = \(π * 2)" // String interpolation
print("Build value: \(buildValue)") // Build value: 7
/*
Optionals are a Swift language feature that either contains a value,
or contains nil (no value) to indicate that a value is missing.
Optionals are a Swift language feature that either contains a value,
or contains nil (no value) to indicate that a value is missing.
A question mark (?) after the type marks the value as optional.
Because Swift requires every property to have a value, even nil must be
@ -82,9 +82,9 @@ if someOptionalString != nil {
someOptionalString = nil
/*
To get the underlying type from an optional, you unwrap it using the
force unwrap operator (!). Only use the unwrap operator if you're sure
the underlying value isn't nil.
Trying to use ! to access a non-existent optional value triggers a runtime
error. Always make sure that an optional contains a non-nil value before
using ! to force-unwrap its value.
*/
// implicitly unwrapped optional