@selector 里面的方法名加参数

 iPhone: NSTimer and that thing called userInfo

Tuesday, May 12, 2009   

As I am implementing some stuff, I had reason to send along some information to a NSTimer's "onComplete" method. Every example online I've seen recently using NSTimer sets the userInfo property to nil. Not very useful for me to learn from. After a little banter on an email list, I understand how this thing works.

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
 UITableViewCell *newCell = [tableView cellForRowAtIndexPath:indexPath];
 UILabel *cellLabel = (UILabel *)[newCell.contentView viewWithTag:1]; 
 [newCell setSelected:YES animated:YES];
 
 NSMutableDictionary *myDictionary = [[NSMutableDictionary alloc] init];
 [myDictionary setObject:tableView forKey:@"table"];
 [myDictionary setObject:indexPath forKey:@"indexPath"];
 // The colon after the onTimer allows for the argument
 [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(onTimer:) userInfo:myDictionary repeats:NO];
 [myDictionary release];
}

So the onTimer method will get called after .5 seconds and it's being sent the userInfo object containing that NSMutableDictionary. Now to use that...

- (void)onTimer:(NSTimer *)timer {
 NSLog(@"--- %@", [timer userInfo] );
 [[[timer userInfo] objectForKey:@"table"] deselectRowAtIndexPath:[[timer userInfo] objectForKey:@"indexPath"] animated:YES];
        // I have a reference to the tableView so I can do this below
        // but to show how the keys work, the call above these works
 //[table deselectRowAtIndexPath:[[timer userInfo] objectForKey:@"indexPath"] animated:YES];
}

Ta da. Now I see how this works, and userInfo has a type of (id) meaning it can be anything.

果然可行

[NSTimer scheduledTimerWithTimeInterval:0.25 target:self selector:@selector(handleTimer:) userInfo:@"参数" repeats:YES];
用的时候只要在下面函数里调用强制转换的userinfo就行，
-(void)handleTimer:(NSTimer*)timer
{
//这里使用(NSString *)[timer userInfo]
}