IOS多线程

IOS异步处理：

dispatch_async(dispatch_get_global_queue(0, 0), ^{ //这里提示错误：Incompatible block pointer types passing 'BOOL (^)(void)' to parameter of type 'dispatch_block_t _Nonnull' (aka 'void (^)(void)')

    return YES;//最终发现错误原因是这里有返回值；
// 处理耗时操作的代码块... 
//通知主线程刷新 
dispatch_async(dispatch_get_main_queue(), ^{ 
//回调或者说是通知主线程刷新， 
}); 
});//这里提示错误：Non-void block does not return a value in all control paths

在第一行提示错误：Incompatible block pointer types passing ‘BOOL (^)(void)’ to parameter of type ‘dispatch_block_t _Nonnull‘ (aka ‘void (^)(void)’)

在最后一行提示错误：Non–void block does not return a value in all control paths

最终是因为异步处理过程中有返回值，所以导致异步块中莫名其妙的错误。