ambertch - Developer IT

Need advice on speeding up tableViewCell photo loading performance

- by ambertch

I have around 20 tableview cells that each contain a number (2-5) thumbnail sized pictures (they are VERY small Facebook profile pictures, ex. http://profile.ak.fbcdn.net/hprofile-ak-sf2p/hs254.snc3/23133_201668_2989_q.jpg). Each picture is an UIImageView added to the cell's contentview. Scrolling performance is poor, and measuring the draw time I've found the UIImage rendering is the bottleneck. I've researched/thought of some solutions but as I am new to iphone development I am not sure which strategy to pursue: preload all the images and retrieve them from disk instead of URL when drawing cells (I'm not sure if cell drawing will still be slow, so I want to hold off on the time investment here) Have the cells display a placeholder image from disk, while the picture is asynchronously loaded (this seems to be the best solution, but I'm currently not sure exactly how to do best do this) There's the fast drawing recommendation from Tweetie, but I don't know that will have much affect if it turns out my overhead is in network loading (http://blog.atebits.com/2008/12/fast-scrolling-in-tweetie-with-uitableview/) Thoughts/implementation advice? Thanks!

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Rails can't render polymorphic associations to XML?

- by ambertch

When I render XML with an :include clause for a polymorphic association I have, it doesn't work. I end up with the XML returning the object pointers instead of the actual objects, like: <posts> #<Comment:0x102ed1540>#<Comment:0x102ecaa38>#<Comment:0x102ec7fe0>#<Comment:0x102ec3cd8> </posts> Yet as_json works! When I render JSON with :include clause, the associations are rendered correctly and I get something like: posts":[ {"type":"Comment","created_at":"2010-04-20T23:02:30-07:00","id":7,"content":"fourth comment"}, {"type":"Comment","created_at":"2010-04-20T23:02:26-07:00","id":6,"content":"third comment"}] My current workaround is using XML builder, but I'm not too comfortable with that in the long run. Does anyone happen to know about this issue? I'm kind of in a catch-22 because while XML doesn't render the associations, as_json doesn't render in a kosher json format (returns an array rather than a list of hashes as proper json should) and the deserializer I'm using on the client side would require modification to parse the json correctly.

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Assigning a view controller to be the delegate of a subview which is not directly descendent?

- by ambertch

I am writing an iphone app where in numerous cases a subview needs to talk to its superview. For example: View A has a table view that contains photos A has a subview B which allows users to add photos, upon which I want to auto append them to A's table view So far I have been creating a @protocol in B, and registering A as the delegate. The problem in my case is that B has a subview C that allows users to add content, and I want actions in C to invoke changes in its grandparent, A. Currently I am working around this by passing around a self pointer to my base view controller (C.delegate = B.delegate), but it doesn't seem very proper to me. Any thoughts? (and/or general advice on code organization when all sort of subviews needs to talk to superviews would be greatly appreciated) Thanks!

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@dynamic property needs setter with multiple behaviors

- by ambertch

I have a class that contains multiple user objects and as such has an array of them as an instance variable: NSMutableArray *users; The tricky part is setting it. I am deserializing these objects from a server via Objective Resource, and for backend reasons users can only be returned as a long string of UIDs - what I have locally is a separate dictionary of users keyed to UIDs. Given the string uidString of comma separated UIDs I override the default setter and populate the actual user objects: @dynamic users; - (void)setUsers:(id)uidString { users = [NSMutableArray arrayWithArray: [[User allUsersDictionary] objectsForKeys:[(NSString*)uidString componentsSeparatedByString:@","]]]; } The problem is this: I now serialize these to database using SQLitePO, which stores these as the array of user objects, not the original string. So when I retrieve it from database the setter mistakenly treats this array of user objects as a string! Where I actually want to adjust the setter's behavior when it gets this object from DB vs. over the network. I can't just make the getter serialize back into a string without tearing up large code that reference this array of user objects, and I tried to detect in the setter whether I have a string or an array coming in: if ([uidString respondsToSelector:@selector(addObject)]) { // Already an array, so don't do anything - just assign users = uidString but no success... so I'm kind of stuck - any suggestions? Thanks in advance!

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issue with tab bar view displaying a compound view

- by ambertch

I created a tab bar application, and I make the first tab a table. So I create a tableView controller, and go about setting the class identity of the view controller for the first tab to my tableView controller. This works fine, and I see the contents of the table filling up the whole screen. However, this is not what I actually want in the end goal - I would like a compound window having multiple views: - the aforementioned table - a custom view with data in it So what I do is create a nib for this content (call it contentNib), change the tab's class from the tableView controller to a generic UIViewController, and set the nib of that tab to this new contentNib. In this new contentNib I drag on a tableView and set File's Owner to the TableViewController. I then link the dataSource and delegate to file's owner (which is TableViewController). Surprisingly this does not work and I receive the error: **Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UIViewController tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x3b0f910'** This is bewildering to me since the file's owner is the TableViewController, which has been assigned to be both the dataSource and delegate. Does someone have either insight into my confusions, or a link to an example of how to have a compound view include a tableView? *update* I see this in the Apple TableView programming guide: "Note: You should use a UIViewController subclass rather than a subclass of UITableViewController to manage a table view if the view to be managed is composed of multiple subviews, one of which is a table view. The default behavior of the UITableViewController class is to make the table view fill the screen between the navigation bar and the tab bar (if either are present)." <----- I don't really get what this is telling me to do though... if someone can explain or point me to an example I'd be much appreciated!

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Using local configs in a Heroku deployment environment

- by ambertch

I'm trying to migrate my app to Heroku - I have a config file that varies with development/staging/production environments as it contains uniquely assigned keys (from Facebook, S3, etc.), so I keep it out of the repository and keep the configs local. As such I'm trying to find a solution for Heroku to have that config file since Heroku deploys from the repository. I noticed Heroku deploys from the master branch - can it deploy from another branch? Because then I could commit the Heroku configs there, and have it not overwrite the other environments' configs every time it pulls. Thanks!

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Rails log management

- by ambertch

I'm starting to get overwhelmed using VI to search through my logs to chase down login errors and would like a better solution. I know Newrelic is highly recommended, though was wondering if there was something free I could try for the short term. Thanks!

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