IOS dispatch_once
来源:互联网 发布:德国拜发测毒素软件 编辑:程序博客网 时间:2024/06/07 17:25
dispatch_once
Executes a block object once and only once for the lifetime of an application.
<span style="font-size: 18px;"> void dispatch_once( dispatch_once_t *predicate, dispatch_block_t block);</span>
Parameters
- predicate
A pointer to a
dispatch_once_t
structure that is used to test whether the block has completed or not.- block
The block object to execute once.
Discussion
This function is useful for initialization of global data (singletons) in an application. Always call this function before using or testing any variables that are initialized by the block.
If called simultaneously from multiple threads, this function waits synchronously until the block has completed.
The predicate must point to a variable stored in global or static scope. The result of using a predicate with automatic or dynamic storage is undefined.
dispatch_once不仅意味着代码仅会被运行一次,而且还是线程安全的,这就意味着你不需要使用诸如@synchronized之类的来防止使用多个线程或者队列时不同步的问题。
如果你要共享某个实例
+(MyInstance*)shareMyInstance()
{
static MyInstance *inst=nil;
static dispatch_once_t p;
dispatch_once(&p,^{
inst=[[MyInstance alloc]init];
});
return inst;
}
你任何时候访问共享实例,需要做的仅是:
MyInstance *myInst = [MyInstance shareMyInstance];
- IOS dispatch_once
- IOS dispatch_once
- iOS dispatch_once详解
- IOS 用dispatch_once创建单利
- IOS多线程之dispatch_once剖析
- iOS-GCD多线程之dispatch_once
- dispatch_once
- dispatch_once
- dispatch_once
- dispatch_once
- dispatch_once
- dispatch_once
- IOS开发之dispatch_once创建单例
- 【ios】利用dispatch_once创建单例
- iOS系统GCD学习(7):dispatch_once
- iOS系统GCD学习(7):dispatch_once
- IOS开发之dispatch_once创建单例
- IOS--dispatch_once 创建单例singletons
- 对象迁移表空间引出的三个小问题
- 学习python入门(一)
- 划分树 hdu2665 第k小
- PHP empty、isset、isnull的区别
- 基于webpack搭建前端工程解决方案探索
- IOS dispatch_once
- 【安卓基础四】adb命令使用Heap检测和分析Android应用内存
- Linux多线程及同步
- PHP字符串函数
- shell 编程笔记
- hiho1031 01背包
- PHP log相关函数
- ios 进阶 -- 开机视频
- 杭电1230