title = "aaaaaa"
//获取字符串的子串
let s = "abcdefg"
var s2 = s.substring(from: s.index(s.startIndex,offsetBy: 3))
print("s2 = \(s2)")
//这里只能使用..< 范围操作符,而不能使用...
let range = s.index(s.startIndex,offsetBy: 3) ..< s.index(s.startIndex,offsetBy: 6)
print("range = \(range)")
s2 = s.substring(with: range)
print("s2 = \(s2)")
//搜索指定子串
let index = s.range(of: "def")?.lowerBound
if let idx = index {
let postion = s.distance(from: s.startIndex, to: idx)
print("postion is:\(postion)")
}else{
print("String not found");
}
struct TestStruct { var a: Int32 = 0; var b: Double = 0.0 }
let obj = TestStruct()
// 获取一个对象的大小
let size = MemoryLayout.size(ofValue: obj)
// 获取一个对象起始地址的字节对齐大小
let align = MemoryLayout.alignment(ofValue: obj)
// 获取一个对象倘若放在一个数组中，那么相邻两个元素之间的字节数（跨度）
let stride = MemoryLayout.stride(ofValue: obj)
print("size of obj: \(size)") // 16
print("alignment of obj: \(align)") // 8
print("stride of obj: \(stride)") // 16
结果
屏幕快照 2016-12-19 下午2.40.01.png
