我希望收到写入给定文件的通知——无需轮询,无需从文件中读取,也无需监视父目录和查看文件修改时间戳。我怎么做?
问问题
2767 次
2 回答
9
我找不到一个简单的例子,所以我贡献了我想出的东西以供将来参考:
@interface FileWatch ()
@property(assign) dispatch_source_t source;
@end
@implementation FileWatch
@synthesize source;
- (id) initWithPath: (NSString*) path targetQueue: (dispatch_queue_t) queue block: (dispatch_block_t) handler
{
self = [super init];
int descriptor = open([path fileSystemRepresentation], O_EVTONLY);
if (descriptor < 0) {
return nil;
}
[self setSource:dispatch_source_create(DISPATCH_SOURCE_TYPE_VNODE, descriptor, DISPATCH_VNODE_WRITE, queue)];
dispatch_source_set_event_handler(source, handler);
dispatch_source_set_cancel_handler(source, ^{
close(descriptor);
});
dispatch_resume(source);
return self;
}
- (void) dealloc
{
if (source) {
dispatch_source_cancel(source);
dispatch_release(source);
source = NULL;
}
}
@end
于 2012-07-12T08:26:47.887 回答
4
根据我的经验,在某些情况下,文件不仅被写入,而且被删除然后重写(某些 plist 文件的情况)。然后你必须稍微修改一下代码:当文件被替换时再次调用该方法以保持监控。
- (void) myMonitoringMethodWithPath: :(NSString*) path
__block typeof(self) blockSelf = self;
__block dispatch_source_t source = dispatch_source_create(DISPATCH_SOURCE_TYPE_VNODE,fildes, DISPATCH_VNODE_DELETE | DISPATCH_VNODE_WRITE | DISPATCH_VNODE_EXTEND | DISPATCH_VNODE_ATTRIB | DISPATCH_VNODE_LINK | DISPATCH_VNODE_RENAME | DISPATCH_VNODE_REVOKE,
queue);
dispatch_source_set_event_handler(source, ^
{
unsigned long flags = dispatch_source_get_data(source);
//Do some stuff
if(flags & DISPATCH_VNODE_DELETE)
{
[blockSelf myMonitoringMethodWithPath:path];
}
});
dispatch_source_set_cancel_handler(source, ^(void)
{
close(fildes);
});
dispatch_resume(source);
}
于 2012-07-12T16:25:21.137 回答