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Search found 236 results on 10 pages for 'mystify'.

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• How to use iPhone OS 3.2 functionality in an iPhone OS 3.0 app?

  - by mystify

  Problem: My app must run on iPhone OS 3.0. However, there are some features of iPhone OS 3.2 which I really want to use. Just as a little add-on for free. But I don't want to cut off my user base by doing this. Imagine you're an iPhone OS 3.0 thing, and someone gives you a book to read. It has iPhone OS 3.2 instructions. You never learned those. So what do you do? Crash? They would have to be hidden, so you're not bothered. Someone wrote recently on SO: keep in mind that you have to check the version at places in the source code where you like to use the new features and provide alternatives for older os versions So how could I do that? Wouldn't Xcode throw warnings when it finds stuff that isn't linkable from anything anywhere? Would I just check for the OS version and dynamically link - somehow - to whatever stuff I think is cool?

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• How to make a view which covers whe whole screen, including the status bar?

  - by mystify

  I want to make an overlay which is partially transparent, and covers the entire screen including the status bar. I've seen that the folks at tapbots do exactly that. So it must be possible somehow.

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• does clipsToBounds = YES reduce my memory footprint?

  - by mystify

  I have a pretty big view which is like 1000 x 1000. So I did clipToBounds = YES. Will this actually produce smaller bitmaps for the views?

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• UITableView Scrolling Performance and semitransparent views - does it matter only in the table?

  - by mystify

  I have a UITableView which only takes like 3/4 of the screen, but not the entire screen. Now I wonder if it matters to scrolling performance a lot, if outside the UITableView there are views with alpha 0.5? When a table view scrolls, is the entire screen affected with compositing and drawing, or only the frame of the table view?

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• How to calculate end-point at a given center plus an radius and angle?

  - by mystify

  I'm trying to do some basic quartz core drawing with arcs, but have an F in math ;-) I have a point: CGPoint center = CGPointMake(100.0f, 100.0f); CGFloat radius = 50.0f; CGFloat startAngle = 20.0f / 180.0f * M_PI; CGFloat endAngle = 150.0f / 180.0f * M_PI; CGContextAddArc(c, center.x, center.y, radius, startAngle, endAngle, 0); Now I want to draw a little dot on the middle of the arc. I mean, not the center point, but the little curve (arc) which is made up between the angles 20-150 degrees. I looked into quartz but unfortunately, there seems no helper function to calculate this. Probably some hardcore trigonometric logic with atan and stuff of this kind needed?

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• Is there an autorelease pool in class methods?

  - by mystify

  I have an class method which generates an UIView, like this: + (UIImage*)imageWithFileName:(NSString*)imgFile { UIImage *img = nil; NSBundle *appBundle = [NSBundle mainBundle]; NSString *resourcePath = [appBundle pathForResource:imgFile ofType:nil]; if (resourcePath != nil) { NSURL *imageURL = [NSURL fileURLWithPath:resourcePath]; NSData *data = [[NSData alloc] initWithContentsOfURL:imageURL]; img = [UIImage imageWithData:data]; // should be autoreleased!! [data release]; } return img; } However, when I use this, the image data is NEVER freed. There is definitely a memory bug with this, although I didn't break any memory management rule I am aware of. My guess is that because this is a class method which gets called from instance methods, There is no active autorelease pool in place or it's one that only gets drained when I quit the app. Could that be right?

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• Are there concurrency problems when using -performSelector:withObject:afterDelay: ?

  - by mystify

  For example, I often use this: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:someDelay]; Now, lets say I call this 10 times to perform at the exact same delay, like: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; - (void)doSomethingAfterDelay:(id)someObject { /* access an array, read stuff, write stuff, do different things that would suffer in multithreaded environments .... all operations are nonatomic! */ } I have observed pretty strange behavior when doing things like this. For my understanding, this method schedules a timer to fire on the current thread, so in this case the main thread. But since it doesn't create new threads, it actually should not be possible to run into concurrency problems, right?

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• Are there concurrency problems when using -performSelector:withObject:afterDelay: ?

  - by mystify

  For example, I often use this: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:someDelay]; Now, lets say I call this 10 times to perform at the exact same delay, like: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; - (void)doSomethingAfterDelay:(id)someObject { /* access an array, read stuff, write stuff, do different things that would suffer in multithreaded environments .... all operations are nonatomic! */ } I have observed pretty strange behavior when doing things like this. For my understanding, this method schedules a timer to fire on the current thread, so in this case the main thread. But since it doesn't create new threads, it actually should not be possible to run into concurrency problems, right?

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• How to make an mutable C array for this data type?

  - by mystify

  There's this instance variable in my objective-c class: ALuint source; I need to have an mutable array of OpenAL Sources, so in this case probably I need a mutable C-array. But how would I create one? There are many questions regarding that: 1) How to create an mutable C-array? 2) How to add something to that mutable C-array? 3) How to remove something from that mutable C-array? 4) What memory management pitfalls must I be aware of? Must i free() it in my -dealloc method? And yes, I think this is something for the nice community wiki...

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• What does the extern keyword mean?

  - by mystify

  What does the extern keyword mean? I've seen that in front of an function declaration like extern void DoFoo ...

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• Why can't I make my parameter like this?

  - by mystify

  - (void)setPropertyValue:(const *void)inValue forID:(UInt32)propertyID { } The compiler doesn't like the const *void, for some reason. When I have that, it says: error: expected ')' before 'void' When I make the parameter like (UInt32)foo there is no problem. Does const *void only work in functions? I need a parameter which can be a "pointer to anything" like UInt32, Float64, etc.

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• How to get notified when the status bar height changes?

  - by mystify

  Does the OS send notifications when the status bar height changes? For example that fat in-call status bar?

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• How to make a dump of the current NSUserDefaults standardUserDefaults state to disk and read back in

  - by mystify

  I want to have some way of backing up the user defaults to a property list or XML, or some other appropriate file format that can be transfered over the net. How could I get a backup of these so that I can send them to a webserver and retrieve them back to the device and read them in to the user defaults database?

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• How to control wether or not my app will stop any iPod music playing?

  - by mystify

  When my app launches, there are rumors that I can decide if any currently playing music is stopped or not. My goal is to use Audio Queue Services, because I believe that's the most powerful audio technology in iPhone OS. So, could I really decide that when my app launches? How? Which one of the many audio technologies on the iPhone OS is responsible for managing this?

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• Which are the most noteable things which make working with Core Date so different than with MySQL?

  - by mystify

  One thing I have in mind is, that datasets in Core Data (or lets say: managed objects) have no ID like known from other databases such as MySQL. Also, they're not in a specific guaranteed order. What else makes Core Data much more "special" compared to working with a relational database like MySQL? Besides the whole object graph persisting and ORM stuff?

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• How to figure out if two CGRect intersect?

  - by mystify

  In -drawRect: I want to check if the provided rect intersects with anotherRect. I'm not good at this geometry math stuff and especially at english so what I want to say is: If you have two sheets of paper on the desk, and one of them covers the other either completely or just a small portion, it is rectsIntersect = YES. How to check that out for rect and anotherRect?

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• How long would I have to wait until Apple releases the WWDC 2010 videos for buying online?

  - by mystify

  How long would I have to wait until Apple releases the WWDC 2010 videos for buying online?

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• How to calculate how many business days are between two dates?

  - by mystify

  A friend asked me yesterday if this was possible on the iPhone. I took a look at NSCalendar and all the related Classes but couldn't find a solution to this. So I thought about this approach: If I had two dates dateA and dateB, I would have to make a for-loop and iterate over every single day in this interval. Then I would count the business days monday until friday, and return the result. Then I went to bed, and I woke up with this probably much better idea: I need to know what day is it when I start. Lets say it's thursday. And then I must know how many days are in that interval. The last part is not hard to figure out. For the first part, I have no clue yet, but I believe there's an day of week value in NSCalendar. With that, I could do some simple math to calculate the amount of business days. Did anyone do that already on the iPhone?

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• How to map an property of ClassA to one of SuperclassA?

  - by mystify

  I have a class named SuperclassA, and an class named ClassA. ClassA inherits from SuperclassA. SuperclassA has got an property called something, so a very generic not-much-saying name. In ClassA, I want to have an property which maps to that something of SuperclassA. How could I do that? I want to make absolutely sure that any access to myBetterProperty results in accessing what's behind something. Assigning an value to myBetterProperty should result in assigning one to something, and vice versa. How to? Pointers set up in init? How would that look like? *self.myBetterProperty = &something; ? I'm not sure about that...

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• What are the relevant classes / frameworks when I want to write / read stuff to / from disk?

  - by mystify

  Which classes / frameworks must I look at? I don't want to use 3rd party libs, so just plain old, boring default solutions to read / write text files and stuff like that... Is there something like a File IO framework?

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• Safe way of iterating over an array or dictionary and deleting entries?

  - by mystify

  I've heard that it is a bad idea to do something like this. But I am sure there is some rule of thumb which can help to get that right. When I iterate over an NSMutableDictionary or NSMutableArray often I need to get rid of entries. Typical case: You iterate over it, and compare the entry against something. Sometimes the result is "don't need anymore" and you have to remove it. But doing so affects the index of all the rows, doesn't it? So how could I safely iterate over it without accidently exceeding bounds or jumping over an element that hasn't been checked?

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• Which methods are good to overwrite when creating custom NSManagedObject subclasses?

  - by mystify

  The Core Data Programming Guide talks a lot about what not to overwrite. So the question is: What is good to overwrite? Like I see it, I can't overwrite -init or -initWithEntity:insertIntoManagedObjectContext: So where else would be a good overwrite point to set up some basic stuff? Or is it generally not needed to do custom initialization? Does the whole thing rely only on accessing properties which then start to do fancy things? So no custom initializations?

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• Is contentOffset the right property to determine the scrolling position of the scroll view?

  - by mystify

  I need to get the current scrolling position of an UIScrollView. How could I do that?

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• Where to read the provided height value in an UITableViewCell?

  - by mystify

  I made a UITableViewCell subclass, and now I want that subclass to be "clever". It should align it's contents to the height of the row. But for this, the cell must know what height value was provided for it in this method: - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath However, no matter what value I assign here, my cell's frame is 44 px height at initialization time (default style). Is there any way I can get that value from the cell at initialization time?

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• Where exactly must I create the fr.lproj localization file, for example?

  - by mystify

  Do you put it in "Other Resources"? Or "Resources-iPhone"? Or even in the Classes group? Or in the root of the project? What's the recommended place?

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