Thread safety, some basic questions about accessing mutable objects across threads
Hi, Please look at the following situations: 1. Created a mutable array in main thread, can I read its values in a secondary thread safely, while no other thread is modifying this mutable array? 2. I need to add objects to this mutable array from a secondary thread, and no other thread is modifying it. Can I simply add an object like, [array addObject:obj]; or if this is wrong how to achieve the same? The object to add is mostly NSString or NSNumber or a mutable dictionary of NSString and NSNumber. Please help. Best, Nick ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Thread safety, some basic questions about accessing mutable objects across threads
Nick,
In your secondary you can use dispatch_async or dispatch_sync to schedule a
block of code to execute on the main thread. Below is a simple example:
dispatch_async(dispatch_get_main_queue(), ^{
// put your code to modify mutable array here
});
I hope this helps.
Thanks,
Abdul
On Aug 6, 2013, at 11:39 AM, Nick Rogers
roger...@mac.commailto:roger...@mac.com wrote:
Hi,
Please look at the following situations:
1. Created a mutable array in main thread, can I read its values in a secondary
thread safely, while no other thread is modifying this mutable array?
2. I need to add objects to this mutable array from a secondary thread, and no
other thread is modifying it. Can I simply add an object like, [array
addObject:obj]; or if this is wrong how to achieve the same? The object to add
is mostly NSString or NSNumber or a mutable dictionary of NSString and NSNumber.
Please help.
Best,
Nick
___
Cocoa-dev mailing list
(Cocoa-dev@lists.apple.commailto:Cocoa-dev@lists.apple.com)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at
cocoa-dev-admins(at)lists.apple.comhttp://lists.apple.com/
Help/Unsubscribe/Update your Subscription:
https://lists.apple.com/mailman/options/cocoa-dev/asowayan%40vectorworks.net
This email sent to asowa...@vectorworks.netmailto:asowa...@vectorworks.net
___
Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
Re: Thread safety, some basic questions about accessing mutable objects across threads
On Aug 6, 2013, at 8:39 AM, Nick Rogers roger...@mac.com wrote: Hi, Please look at the following situations: 1. Created a mutable array in main thread, can I read its values in a secondary thread safely, while no other thread is modifying this mutable array? Yes, but the second half of that sentence is the tricky part. One typically uses a lock to ensure that no other threads are modifying the array. 2. I need to add objects to this mutable array from a secondary thread, and no other thread is modifying it. Can I simply add an object like, [array addObject:obj]; or if this is wrong how to achieve the same? The object to add is mostly NSString or NSNumber or a mutable dictionary of NSString and NSNumber. Yes, NSArray can be used from any thread, as long as if one thread is modifying the array it is the only thread accessing the array. Again, you need to use a synchronization primitive to ensure this is the case. --Kyle Sluder ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Thread safety, some basic questions about accessing mutable objects across threads
On Aug 6, 2013, at 8:39 AM, Nick Rogers roger...@mac.com wrote: 1. Created a mutable array in main thread, can I read its values in a secondary thread safely, while no other thread is modifying this mutable array? Yes. Most non-thread-safe objects don’t care what threads you call them on, so long as they’re only called on one thread at a time. So you can use locks or @synchronized blocks to coordinate access. (The exceptions are higher-level things that use runloops or dispatch queues, such as NSURLConnection, NSStream, etc. Those usually need to be called only from the same thread/queue they’re scheduled on, because they’re also getting callbacks on that same thread/queue.) —Jens ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Thread safety, some basic questions about accessing mutable objects across threads
On Aug 6, 2013, at 8:39 AM, Nick Rogers roger...@mac.com wrote: 1. Created a mutable array in main thread, can I read its values in a secondary thread safely, while no other thread is modifying this mutable array? 2. I need to add objects to this mutable array from a secondary thread, and no other thread is modifying it. Can I simply add an object like, [array addObject:obj]; or if this is wrong how to achieve the same? The object to add is mostly NSString or NSNumber or a mutable dictionary of NSString and NSNumber. Honestly I would recommend a thread-confinement strategy. If you have some other thread that wants to add an object to the array, it should message the thread that owns that array (I'm guessing the main thread here) and tell it to add the object. TN2109 discusses this strategy along with sample code: http://developer.apple.com/library/ios/#technotes/tn2109/_index.html -- David Duncan ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
