swift語言點評二

一、資料類型

1、基礎類型的封裝

Swift provides its own versions of all fundamental C and Objective-C types, including <code>Int</code> for integers, <code>Double</code>and <code>Float</code> for floating-point values

2、新類型

 Swift introduces advanced types not found in Objective-C, such as tuples.

Tuples enable you to create and pass around groupings of values.

3、類型安全語言

Swift is a type-safe language, which means the language helps you to be clear about the types of values your code can work with.

4、資料類型轉化

<code>let three = 3</code>

<code>let pointOneFourOneFiveNine = 0.14159</code>

<code>let pi = Double(three) + pointOneFourOneFiveNine</code>

<code>// pi equals 3.14159, and is inferred to be of type Double</code>

5、Tuples

<code>let http404Error = (404, "Not Found")</code>

<code>let (statusCode, statusMessage) = http404Error</code>

<code>print("The status code is \(statusCode)")</code>

<code>// Prints "The status code is 404"</code>

<code>print("The status message is \(statusMessage)")</code>

<code>// Prints "The status message is Not Found"</code>

6、Optionals

<code>let possibleNumber = "123"</code>

<code>let convertedNumber = Int(possibleNumber)</code>

　　類型推斷 convertedNumber:Int?

7、Optional Binding

　　if let firstNumber = Int("4")

　　You use optional binding to find out whether an optional contains a value

8、Implicitly Unwrapped Optionals

 . You write an implicitly unwrapped optional by placing an exclamation mark (<code>String!</code>) rather than a question mark (<code>String?</code>) after the type that you want to make optional.

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