swift语言点评十六-Initialization && Deinitialization
initial value:必须初始化、不影响观察者
Classes and structures must set all of their stored properties to an appropriate initial value by the time an instance of that class or structure is created. Stored properties cannot be left in an indeterminate state.
You can set an initial value for a stored property within an initializer, or by assigning a default property value as part of the property’s definition. These actions are described in the following sections.
When you assign a default value to a stored property, or set its initial value within an initializer, the value of that property is set directly, without calling any property observers.
Default Property Values:另一种初始化方式;
Parameter Names and Argument Labels
As with function and method parameters, initialization parameters can have both a parameter name for use within the initializer’s body and an argument label for use when calling the initializer.
Optional Property Types
Properties of optional type are automatically initialized with a value of nil
,
Assigning Constant Properties During Initialization
常量可以在初始化时赋值;
Default Initializers
条件:1、所有参数都有缺省参量;2、没有初始化函数;
Memberwise Initializers for Structure Types
结构体可以有以属性为参量的缺省构造器,类没有;
Initializer Delegation for Value Types:初始化代理
区分于引用类型:值类型、引用类型。
?没有明白?
self.init只能在初始器内部使用。
For value types, you use self.init
to refer to other initializers from the same value type when writing your own custom initializers. You can call self.init
only from within an initializer.
Class Inheritance and Initialization
swift语言点评十六-Initialization && Deinitialization的更多相关文章
- swift语言点评十-Value and Reference Types
结论:value是拷贝,Reference是引用 Value and Reference Types Types in Swift fall into one of two categories: f ...
- swift语言点评十九-类型转化与检查
1.oc比较: -(BOOL) isKindOfClass: classObj判断是否是这个类或者这个类的子类的实例 -(BOOL) isMemberOfClass: classObj 判断是否是这个 ...
- swift语言点评十八-异常与错误
1.错误类型与枚举的结合 enum VendingMachineError: Error { case invalidSelection case insufficientFunds(coinsNee ...
- swift语言点评十四-继承
Overriding A subclass can provide its own custom implementation of an instance method, type method, ...
- swift语言点评十五-$0
import UIKitimport XCPlayground class ViewController: UIViewController { func action() { print(" ...
- swift语言点评十二-Subscripts
Classes, structures, and enumerations can define subscripts, which are shortcuts for accessing the m ...
- Swift语言指南(十)--字符串与字符
原文:Swift语言指南(十)--字符串与字符 字符串是一段字符的有序集合,如"hellow,world"或"信天翁".Swift 中的字符串由 String ...
- swift语言点评二十-扩展
结论:扩展无法修改原来的数据结构. Extensions can add new functionality to a type, but they cannot override existing ...
- swift语言点评六-Numbers and Basic Values
Topics Logical Values struct Bool A value type whose instances are either true or false. Numeric Val ...
随机推荐
- 对ListView的Item子控件监听并跳转页面
public class MyAdapteforOwner extends BaseAdapter{ List<OwnerDevice>datas; private Context con ...
- mac修改默认打开方式
首先选中你要修改默认打开方式的文件,右键单击这个文件,在弹出的菜单中,选择“查看简介”: 然后在弹出的菜单中,找到“打开方式”选项,从下来的菜单中,找到你希望默认打开这个文件的程序: 然后点击下面的“ ...
- MDL的一些理解
驱动程序要操作一个用户模式下的内存(32位下小于2G),那么是有风险的,因为用户模式下当前进程的线程不断切换,用户模式下的地址可能会无效.这时的操作将会有未知结果. 用MDL系统API可以将用户模式下 ...
- JS中let和var的区别
js中let和var定义变量的区别 let变量之前没见过,刚遇到,探探究竟. 以下转自:http://blog.csdn.net/nfer_zhuang/article/details/48781 ...
- BZOJ 4229: 选择 LCT_独创方法_边双
考虑如果两点在一个环中,那么这两点一定可以构出双联通分量. 考虑环和环镶嵌,那么两个环中的点一定都互为双联通分量. 由此,我们想到一个算法: 将删边转为反向加边,用LCT维护图. 当我们连接两个点时, ...
- 2015 Multi-University Training Contest 6 hdu 5358 First One
First One Time Limit: 4000/2000 MS (Java/Others) Memory Limit: 131072/131072 K (Java/Others)Total ...
- centos7修改网卡名
http://blog.csdn.net/henulwj/article/details/47061023
- 110_leetcode_Best Time to Buy and sell Stock II
Say you have an array for which the ith element is the price of a given stock on day i. Design an al ...
- nodeJS npm grunt grunt-cli
1.安装好nodeJS后 ,一般都会把npm也安装好的.nodeJs集成npm的,可通过在cmd 分别运行 node -v和 npm -v来查看他们的版本,假设显示可说明可继续以下的操作 2.想安装g ...
- System.getProperty()方法可以获取的值
/** 获得当前类的完整路径.最后一句 */ package org.outman.dms.server; import java.net.MalformedURLException; import ...