Merge pull request #10576 from lujun9972/add-MjAxODEwMDMgSW50cm9kdWNpbmcgU3dpZnQgb24gRmVkb3JhLm1kCg==

选题: Introducing Swift on Fedora

sources/tech/20181003 Introducing Swift on Fedora.md

@@ -0,0 +1,70 @@
+Introducing Swift on Fedora
+======
+
+![](https://fedoramagazine.org/wp-content/uploads/2018/09/swift-816x345.jpg)
+
+Swift is a general-purpose programming language built using a modern approach to safety, performance, and software design patterns. It aims to be the best language for a variety of programming projects, ranging from systems programming to desktop applications and scaling up to cloud services. Read more about it and how to try it out in Fedora.
+
+### Safe, Fast, Expressive
+
+Like many modern programming languages, Swift was designed to be safer than C-based languages. For example, variables are always initialized before they can be used. Arrays and integers are checked for overflow. Memory is automatically managed.
+
+Swift puts intent right in the syntax. To declare a variable, use the var keyword. To declare a constant, use let.
+
+Swift also guarantees that objects can never be nil; in fact, trying to use an object known to be nil will cause a compile-time error. When using a nil value is appropriate, it supports a mechanism called **optionals**. An optional may contain nil, but is safely unwrapped using the **?** operator.
+
+Some additional features include:
+
+  * Closures unified with function pointers
+  * Tuples and multiple return values
+  * Generics
+  * Fast and concise iteration over a range or collection
+  * Structs that support methods, extensions, and protocols
+  * Functional programming patterns, e.g., map and filter
+  * Powerful error handling built-in
+  * Advanced control flow with do, guard, defer, and repeat keywords
+
+
+
+### Try Swift out
+
+Swift is available in Fedora 28 under then package name **swift-lang**. Once installed, run swift and the REPL console starts up.
+
+```
+$ swift
+Welcome to Swift version 4.2 (swift-4.2-RELEASE). Type :help for assistance.
+ 1> let greeting="Hello world!"
+greeting: String = "Hello world!"
+ 2> print(greeting)
+Hello world!
+ 3> greeting = "Hello universe!"
+error: repl.swift:3:10: error: cannot assign to value: 'greeting' is a 'let' constant
+greeting = "Hello universe!"
+~~~~~~~~ ^
+
+
+ 3>
+
+```
+
+Swift has a growing community, and in particular, a [work group][1] dedicated to making it an efficient and effective server-side programming language. Be sure to visit [its home page][2] for more ways to get involved.
+
+Photo by [Uillian Vargas][3] on [Unsplash][4].
+
+
+--------------------------------------------------------------------------------
+
+via: https://fedoramagazine.org/introducing-swift-fedora/
+
+作者：[Link Dupont][a]
+选题：[lujun9972](https://github.com/lujun9972)
+译者：[译者ID](https://github.com/译者ID)
+校对：[校对者ID](https://github.com/校对者ID)
+
+本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
+
+[a]: https://fedoramagazine.org/author/linkdupont/
+[1]: https://swift.org/server/
+[2]: http://swift.org
+[3]: https://unsplash.com/photos/7oJpVR1inGk?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText
+[4]: https://unsplash.com/search/photos/fast?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText