//MARK:-------swift中的typedef--------------//使用 keyword定义类型别名，相似typedeftypealias NSInteger = Intvar value : NSInteger = 45value = 12print(value);//MARK:-------String--------------let label = "The width is "let width = 94var widthLabel = label + String(width)  //Swift不支持隐式类型转换。须要显式类型转换widthLabel += "!"print(widthLabel)//Swift使用\(item)的形式进行字符串格式化let apples = 3let oranges = 5let appleSummary = "I have \(apples) apples."let fruitSummary = "I have \(apples + oranges) pieces of fruit."