swift语言点评二

一、数据类型

1、基础类型的封装

Swift provides its own versions of all fundamental C and Objective-C types, including Int for integers, Doubleand Float for floating-point values

2、新类型

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

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

3、类型安全语言

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、数据类型转化

1. let three = 3
2. let pointOneFourOneFiveNine = 0.14159
3. let pi = Double(three) + pointOneFourOneFiveNine
4. // pi equals 3.14159, and is inferred to be of type Double

5、Tuples

1. let http404Error = (404, "Not Found")

1. let (statusCode, statusMessage) = http404Error
2. print("The status code is \(statusCode)")
3. // Prints "The status code is 404"
4. print("The status message is \(statusMessage)")
5. // Prints "The status message is Not Found"

6、Optionals

1. let possibleNumber = "123"
2. let convertedNumber = Int(possibleNumber)

　　类型推断 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 (String!) rather than a question mark (String?) after the type that you want to make optional.