swift基本数据类型使用

swift基本数据类型的使用之一: 字符串的使用

swift String的使用

1.字符串的定义
1> 不可变字符串的定义
2> 可变字符串的定义
2.获取字符串的长度
3.字符串的拼接
1> 字符串之间的拼接
2> 字符串和其它标识符之间的拼接 "(标识符)"
3> 字符串拼接过程中格式化: String(format:"%d:%d", 参数)
4.字符串的截取
1> 方式一: 将String转成NSString,再进行截取(推荐)
2> 方式二: 直接使用String中方法,进行截取. String.Index

     let str = "Hello Swift"
     // str = "hello Objective-C"

     // 2> 定义可变字符串 : 使用var修饰
     var strM = "Hello World"
     strM = "Hello China"


     // 2.获取字符串的长度
     let length = str.count //str.characters.count


     // 3.字符串的拼接
     // 3.1.字符串之间的拼接
     let str1 = "小码哥"
     let str2 = "IT教育"
     // OC拼接方式 NSString stringwithFormat:@"%@%@", str1, str2
     let str3 = str1 + str2

     // 3.2.字符串和其它标识符之间的拼接
     let name = "why"
     let age = 19
     let height = 1.87

     let infoStr = "my nams is \(name), age is \(age), height is \(height)"

     // 3.3.字符串拼接过程中的格式化: 03:04
     let min = 3
     let second = 4

     let timeStr = String(format: "%02d:%02d", min, second)


     // 4.字符串的截取
     let urlString = "www.sunshine.com"

     // 4.1.方式一:
     // 将String类型转成NSString类型,再进行截取: as NSString
     let header1 = (urlString as NSString).substring(to: 3)
     let range1 = NSMakeRange(4, 5)
     let middle1 = (urlString as NSString).substring(with: range1)
     let footer1 = (urlString as NSString).substring(from: 10)

     // 4.2.方式二:
     // 直接使用String类型方法,进行截取
     let headerIndex = urlString.index(urlString.startIndex, offsetBy: 3)
     let header2 =  String(urlString[..<headerIndex]) //urlString.substring(to: headerIndex)

     let startIndex = urlString.index(urlString.startIndex, offsetBy: 4)
     let endIndex = urlString.index(urlString.startIndex, offsetBy: 9)
     //let range = NSMakeRange(startIndex..<endIndex)
     //Range((startIndex..<endIndex))
     let middle2 = String(urlString[startIndex..<endIndex])//urlString.substring(with: range)

     let footerIndex = urlString.index(urlString.endIndex, offsetBy: -3)
     let footer2 = String(urlString[footerIndex...]) //urlString.substring(from: footerIndex)