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Re: DataSource modified while TableView is displaying data
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Re: DataSource modified while TableView is displaying data


  • Subject: Re: DataSource modified while TableView is displaying data
  • From: Jean Suisse <email@hidden>
  • Date: Fri, 27 Apr 2012 09:42:54 +0200

So if I understand you correctly alteration of the dataSource should always be performed on the main thread.
[implied: because requests for redraw or similar that do not come from my code will always run on the main thread. Is that right ?].

Done. Not easy, but done. (Things were a little more complicated than just dispatching a block).

Now, for the sake of knowledge, I would like to consider the case where I can't always alter the datasource on the main thread. What then ?
I recall assembly instructions (STI, CLI) to prevent IRQ from occurring inside a few line of code.
Is there some way to prevent thread switching for a short time ? Do you know an other way to deal with the present issue (alteration of the dataSource of an NSTableView not performed on the main thread) ?

Jean

On 26 avr. 2012, at 21:47, Corbin Dunn wrote:

>
> On Apr 26, 2012, at 3:23 AM, Jean Suisse <email@hidden> wrote:
>
>> Dear Peter,
>>
>> Thank you for your reply. Here is the requested code (see below).
>> After more investigations, I would like to take back a previous statement, that the tableview was perfectly aware that the number of rows in the DS was changed. This is due to my inexperience in stepping through the code across multiple threads.
>>
>> Here are the facts :
>>
>> - Only the controller removes rows from the datasource. Either in response to user actions (canceling tasks) or as a result of a Task completed notification from a running task.
>> - Each change in the dataSource is immediately followed by a reloadData message sent to the TableView.
>> - Sometimes, randomly, the TableView requests a row index that is out of bounds by one index (e.g. row #5 when the dataSource contains only 5 elements).
>>
>> I am thinking that a redraw occurs in-between the removal of one element of the table and the reloadData message.
>> For now, I did a quick fix for this issue by adding a category with "safeObjectAtIndex"…. But one way to be certain would be to ensure that the two messages (removal + reloadData) are sent without any thread/process switching occurring…
>>
>> The code for numberOfRowsInTableView : (experimentList is an instance of NSMutableAray)
>>
>> - (NSInteger)numberOfRowsInTableView:(NSTableView*)tableView
>> {
>> 	return self.experimentList ? [self.experimentList count] : 0;
>> }
>
> This is fine as long as your experimentList is only ever modified on the main thread.
>
> It sounds like that isn't the case, which is why you have random problems.
>
> corbin
>
>
>>
>> Jean
>>
>>
>> On 26 avr. 2012, at 11:45, Peter Hudson wrote:
>>
>>>
>>> Can you post your code for     numberOfRowsInTableView:
>>>
>>> Peter
>>
>>
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  • Follow-Ups:
    • Re: DataSource modified while TableView is displaying data
      • From: Scott Ribe <email@hidden>
    • Re: DataSource modified while TableView is displaying data
      • From: Roland King <email@hidden>
References: 
 >Re: DataSource modified while TableView is displaying data (From: Peter Hudson <email@hidden>)
 >Re: DataSource modified while TableView is displaying data (From: Jean Suisse <email@hidden>)
 >Re: DataSource modified while TableView is displaying data (From: Corbin Dunn <email@hidden>)

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