IOS --- Singleton Mode

IOS --- Singleton Mode

Dispatch_once

The dispatch_once function is an API that only executes the specified processing once during application execution. The following Frequently-seen source code for initialization can be simplified through the dispatch_once function:

Static int initialized = NO; if (initalized = NO) {/** initialize */initialized = YES ;}

If the dispatch_once function is used, the source code is changed:

Static dispatch_once_t pred; dispatch_once (& pred, ^ {/** initialization */});

The source code does not seem to change much. However, through the dispatch_once function, the source code can be fully secure even if it is executed in a multi-threaded environment.