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« στις: Μάιος 07, 2016, 04:28:49 μμ »
Too many people ask us: What is the swift language?

Swift is a programming language for iOS, OS X, watchOS, and tvOS apps that builds on the best of C and Objective-C, without the constraints of C compatibility. Swift adopts safe programming patterns and adds modern features to make programming easier, more flexible, and more fun. Swift’s clean slate, backed by the mature and much-loved Cocoa and Cocoa Touch frameworks, is an opportunity to reimagine how software development works.

Apple laid the foundation for Swift by advancing our existing compiler, debugger, and framework infrastructure. We simplified memory management with Automatic Reference Counting (ARC). Our framework stack, built on the solid base of Foundation and Cocoa, has been modernized and standardized throughout. Objective-C itself has evolved to support blocks, collection literals, and modules, enabling framework adoption of modern language technologies without disruption. Thanks to this groundwork, we can now introduce a new language for the future of Apple software development.

It adopts the readability of Objective-C’s named parameters and the power of Objective-C’s dynamic object model. It provides seamless access to existing Cocoa frameworks and mix-and-match interoperability with Objective-C code. Building from this common ground, Swift introduces many new features and unifies the procedural and object-oriented portions of the language.

The compiler is optimized for performance, and the language is optimized for development, without compromising on either. It’s designed to scale from “hello, world” to an entire operating system.

Tradition suggests that the first program in a new language should print the words “Hello, world!” on the screen. In Swift, this can be done in a single line:

    print("Hello, world!")

If you have written code in C or Objective-C, this syntax looks familiar to you in Swift, this line of code is a complete program. You don’t need to import a separate library for functionality like input/output or string handling. Code written at global scope is used as the entry point for the program, so you don’t need a main() function. You also don’t need to write semicolons at the end of every statement.

Κώδικας: [Επιλογή]
//: Simple Values
//: Use `let` to make a constant and `var` to make a variable. The value of a constant doesn’t need to be known at compile time, but you must assign it a value exactly once. This means you can use constants to name a value that you determine once but use in many places.
var myVariable = 42
myVariable = 50
let myConstant = 42
//: A constant or variable must have the same type as the value you want to assign to it. However, you don’t always have to write the type explicitly. Providing a value when you create a constant or variable lets the compiler infer its type. In the example above, the compiler infers that `myVariable` is an integer because its initial value is an integer.
//: If the initial value doesn’t provide enough information (or if there is no initial value), specify the type by writing it after the variable, separated by a colon.
let implicitInteger = 70
let implicitDouble = 70.0
let explicitDouble: Double = 70
//: - Experiment:
//: Create a constant with an explicit type of `Float` and a value of `4`.
//: Values are never implicitly converted to another type. If you need to convert a value to a different type, explicitly make an instance of the desired type.
let label = "The width is "
let width = 94
let widthLabel = label + String(width)
//: - Experiment:
//: Try removing the conversion to `String` from the last line. What error do you get?
//: There’s an even simpler way to include values in strings: Write the value in parentheses, and write a backslash (`\`) before the parentheses. For example:
let apples = 3
let oranges = 5
let appleSummary = "I have \(apples) apples."
let fruitSummary = "I have \(apples + oranges) pieces of fruit."
//: - Experiment:
//: Use `\()` to include a floating-point calculation in a string and to include someone’s name in a greeting.
//: Create arrays and dictionaries using brackets (`[]`), and access their elements by writing the index or key in brackets. A comma is allowed after the last element.
var shoppingList = ["catfish", "water", "tulips", "blue paint"]
shoppingList[1] = "bottle of water"
var occupations = [
    "Malcolm": "Captain",
    "Kaylee": "Mechanic",
occupations["Jayne"] = "Public Relations"
//: To create an empty array or dictionary, use the initializer syntax.
let emptyArray = [String]()
let emptyDictionary = [String: Float]()
//: If type information can be inferred, you can write an empty array as `[]` and an empty dictionary as `[:]`—for example, when you set a new value for a variable or pass an argument to a function.
shoppingList = []
occupations = [:]
//: See [License](License) for this sample's licensing information.
//: [Next](@next)

to be continued