Using performSelector:withObject:afterDelay: with non-object parameters

Question

I want to invoke setEditing:animated: on a table view with a slight delay. Normally, I'd use performSelector:withObject:afterDelay: but

pSwOaD only accepts one parameter
the second parameter to setEditing:animated: is a primitive BOOL - not an object

In the past I would create a dummy method in my own class, like setTableAnimated and then call [self performSelector:@selector(setTableAnimated) withObject:nil afterDelay:0.1f but that feels kludgy to me.

Is there a better way to do it?

score 20 · Accepted Answer · answered Mar 06 '11 at 20:55

20

Why not use a dispatch_queue ?

  double delayInSeconds = 2.0;
  dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
  dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
      [tableView setEditing …];
  });

answered Mar 06 '11 at 20:55

Marcelo Alves

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I don't know why this was down-voted, seems like a good solution to me. – Aidan Steele Mar 06 '11 at 21:31
if you are using iOS4 this is the way to do it – Chris Sep 11 '11 at 19:31

score 17 · Answer 2 · edited May 23 '17 at 11:58

17

You need to use NSInvocation:

See this code, taken from this answer, and I've changed it slightly to match your question:

BOOL yes = YES;
NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[self.tableView methodSignatureForSelector:@selector(setEditing:Animated:)]];
[inv setSelector:@selector(setEditing:Animated:)];
[inv setTarget:self.tableView];
[inv setArgument:&yes atIndex:2]; //this is the editing BOOL (0 and 1 are explained in the link above)
[inv setArgument:&yes atIndex:3]; //this is the animated BOOL
[inv performSelector:@selector(invoke) withObject:nil afterDelay:0.1f];

edited May 23 '17 at 11:58

Community

1
1

answered Mar 06 '11 at 14:22

Jonathan.

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I think using a var name like `BOOL _yes = YES` is a little clearer, since it alleviates a little confusion as to whether you've got a typo (yes vs YES). – gabrielk Jun 08 '14 at 18:01
Also just wanted to point out, the reason for using a variable for `YES` instead of just passing the bool directly: `NSInvocation` throws an exception: `[NSInvocation setArgument:atIndex:]: NULL address argument`, [explained in this answer](http://stackoverflow.com/a/11061349/146517). – gabrielk Jun 08 '14 at 18:05

score 1 · Answer 3 · answered Mar 06 '11 at 13:54

The selector setEditing:animated: is not compatible with performSelector:withObject:afterDelay. You can only call methods with 0 or 1 arguments and the argument (if any) MUST be an object. So your workaround is the way to go. You can wrap the BOOL value in an NSValue object and pass it to your setTableAnimated method.

score 0 · Answer 4 · answered Mar 06 '11 at 15:26

0

If you can get your head around it, use an NSInvocation grabber to make an invocation object & call it with a delay with 1 line instead of many: http://overooped.com/post/913725384/nsinvocation

answered Mar 06 '11 at 15:26

Pierre Houston

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Hardly one line if it involves creating a class. – Jonathan. Mar 06 '11 at 15:28

Using performSelector:withObject:afterDelay: with non-object parameters

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