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  • iOS - How to pass information from the VIEW to the Controller?

    - by user1720503
    I am fairly new to programming in general, and have been following the CS193p videos on iTunesU. I am currently doing assignment 3, and am having trouble getting a bit of information from the View sent to the View Controller. I believe I have set up the whole delegation thing correctly, so the question really is to how to get my View Controller to see a bit of information (such as self.bounds.size.width), which is a property that only the View has. Would this involve using self.dataSource? And if so, through what means could I pass this bit of information? Thanks!!

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  • Fetch request error: no entity? Probably easy, but help!

    - by cksubs
    Hi, I'm going through the Stanford iPhone course. I'm on the second Paparazzi assignment. I'm getting this error: * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'executeFetchRequest:error: A fetch request must have an entity.' I've copied a lot of the code from this walkthrough site. Running his source code works perfectly, and at this point my code is pretty much exactly the same as his. But it throws that error. See below for the relavent bits: // Create FetchRequest NSFetchRequest *request = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:context]; [request setEntity:entity]; // Set the sort descriptor NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"personName" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [request setSortDescriptors:sortDescriptors]; [sortDescriptors release]; [sortDescriptor release]; // set up NSFetchedResultsController to hold the fetch NSFetchedResultsController *frc = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:context sectionNameKeyPath:nil cacheName:@"personCache"]; // execute the fetch NSError *error; NSLog(@"Prints Here"); [frc performFetch:&error]; NSLog(@"Doesn't Print Here"); I'm clearly setting the entity with [request setEntity:entity]. So the error has me stumped. Is there something I'm missing? Maybe in another file? I don't know. I'm still so confused with Objective-C.... Thanks.

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  • Learning Objective-C: Need advice on populating NSMutableDictionary

    - by Zigrivers
    I am teaching myself Objective-C utilizing a number of resources, one of which is the Stanford iPhone Dev class available via iTunes U (past 2010 class). One of the home work assignments asked that I populate a mutable dictionary with a predefined list of keys and values (URLs). I was able to put the code together, but as I look at it, I keep thinking there is probably a much better way for me to approach what I'm trying to do: Populate a NSMutableDictionary with the predefined keys and values Enumerate through the keys of the dictionary and check each key to see if it starts with "Stanford" If it meets the criteria, log both the key and the value I would really appreciate any feedback on how I might improve on what I've put together. I'm the very definition of a beginner, but I'm really enjoying the challenge of learning Objective-C. void bookmarkDictionary () { NSMutableDictionary* bookmarks = [NSMutableDictionary dictionary]; NSString* one = @"Stanford University", *two = @"Apple", *three = @"CS193P", *four = @"Stanford on iTunes U", *five = @"Stanford Mall"; NSString* urlOne = @"http://www.stanford.edu", *urlTwo = @"http://www.apple.com", *urlThree = @"http://cs193p.stanford.edu", *urlFour = @"http://itunes.stanford.edu", *urlFive = @"http://stanfordshop.com"; NSURL* oneURL = [NSURL URLWithString:urlOne]; NSURL* twoURL = [NSURL URLWithString:urlTwo]; NSURL* threeURL = [NSURL URLWithString:urlThree]; NSURL* fourURL = [NSURL URLWithString:urlFour]; NSURL* fiveURL = [NSURL URLWithString:urlFive]; [bookmarks setObject:oneURL forKey:one]; [bookmarks setObject:twoURL forKey:two]; [bookmarks setObject:threeURL forKey:three]; [bookmarks setObject:fourURL forKey:four]; [bookmarks setObject:fiveURL forKey:five]; NSString* akey; NSString* testString = @"Stanford"; for (akey in bookmarks) { if ([akey hasPrefix:testString]) { NSLog(@"Key: %@ URL: %@", akey, [bookmarks objectForKey:akey]); } } } Thanks for your help!

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  • release viewcontroller after presenting modally

    - by Jonathan
    I was watching CS193P Stanford course on Itunes, and in one of the lectures a demo was given and There it was said you could present the viewcontroller modally and then release it. Roughly like this (I know this isn't perfect but I'm on my PC atm) [self.view presentcontentmodally:myVC] [myVC release]; However this seems to produce problems. If I put a NSLog(@"%d", [myVC retainCount]) between those two lines then it returns 2 implying it is ok to release. However when I dismiss the myVC the app crashes. Nothing in the NSlog and the debugger won't show where it stopped. But I used malloc-history or something that some blog said would help. And found that it was the myVC. So should I be releasing myVC? (also when the modalVC has been dissmissed should the app's memory usuage go back to before the modalVC was presented?)

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  • Solving the EXC_BAD_ACCESS in WhatATool Part 2

    - by Allen
    #import <Cocoa/Cocoa.h> @interface PolygonShape : NSObject { int numberOfSides, maximumNumberOfSides, minimumNumberOfSides; } @property (readwrite) int numberOfSides, maximumNumberOfSides, minimumNumberOfSides; @property (readonly) float angleInDegrees, angleInRadians; @property (readonly) NSString * name; @property (readonly) NSString * description; -(id) init; -(void) setNumberOfSides:(int)sides; -(void) setMinimumNumberOfSides:(int)min; -(void) setMaximumNumberOfSides:(int)max; -(float) angleInDegrees; -(float) angleInRadians; -(NSString *) name; -(id) initWithNumberOfSides:(int) sides minimumNumberOfSides:(int) min maximumNumberOfSides:(int) max; -(NSString *) description; -(void) dealloc; @end #import "PolygonShape.h" @implementation PolygonShape -(id) init { return [self initWithNumberOfSides:4 minimumNumberOfSides:3 maximumNumberOfSides:5]; } @synthesize numberOfSides, minimumNumberOfSides, maximumNumberOfSides, angleInRadians; -(void) setNumberOfSides:(int)sides { numberOfSides = sides; NSLog(@"The number of sides is off limit so the number of sides is %@.",sides); } -(void)setMaximumNumberOfSides:(int)max { if (maximumNumberOfSides <= 12) { maximumNumberOfSides = max; } } -(void)setMinimumNumberOfSides: (int)min { if (minimumNumberOfSides > 2) { minimumNumberOfSides = min; } } - (id)initWithNumberOfSides:(int)sides minimumNumberOfSides:(int)min maximumNumberOfSides:(int)max { if(self=[super init]) { [self setNumberOfSides:(int)sides]; [self setMaximumNumberOfSides:(int)max]; [self setMinimumNumberOfSides: (int)min]; } return self; } -(float) angleInDegrees { float anglesInDegrees = (180 * (numberOfSides - 2) / numberOfSides); return anglesInDegrees; } -(float)angleInRadiants { float anglesInRadiants = ((180 * (numberOfSides - 2) / numberOfSides) * (180 / M_PI)); return anglesInRadiants; } -(NSString *)name { NSString * output; switch (numberOfSides) { case 3: output = @"Triangle"; break; case 4: output = @"Square"; break; case 5: output = @"Pentagon"; break; case 6: output = @"Hexagon"; break; case 7: output = @"Heptagon"; break; case 8: output = @"Octagon"; break; case 9: output = @"Nonagon"; break; case 10: output = @"Decagon"; break; case 11: output = @"Hendecagon"; break; case 12: output = @"Dodecabgon"; break; default: output = @"Invalid number of sides: %i is greater than maximum of five allowed."; } return output; } -(NSString *)description { NSString * output; NSLog(@"Hello I am a %i-sided polygon (aka a %@) with angles of %f degrees (%f radians).", numberOfSides, output, [self angleInDegrees], [self angleInRadiants]); return [self description]; } -(void)dealloc { [super dealloc]; } @end #import <Foundation/Foundation.h> #import "PolygonShape.h" void PrintPathInfo() { NSLog(@"Section 1"); NSLog(@"--------------------"); NSString *path = [@"~" stringByExpandingTildeInPath]; NSLog(@"My home folder is at '%@'.", path); NSArray *pathComponent = [path pathComponents]; for (path in pathComponent) { NSLog(@"%@",path); } NSLog(@"--------------------"); NSLog(@"\n"); } void PrintProcessInfo() { NSLog(@"Section 2"); NSLog(@"--------------------"); NSString * processName = [[NSProcessInfo processInfo] processName]; int processIdentifier = [[NSProcessInfo processInfo] processIdentifier]; NSLog(@"Process Name: '%@', Process ID: '%i'", processName, processIdentifier); NSLog(@"--------------------"); NSLog(@"\n"); } void PrintBookmarkInfo() { NSLog(@"Section 3"); NSLog(@"--------------------"); NSArray * keys = [NSArray arrayWithObjects: @"Stanford University", @"Apple", @"CS193P", @"Stanford on iTunes U", @"Stanford Mall", nil]; NSArray * objects = [NSArray arrayWithObjects: [NSURL URLWithString: @"http://www.stanford.edu"], @"http://www.apple.com", @"http://cs193p.stanford.edu", @"http://itunes.stanford.edu", @"http://stanfordshop.com",nil]; NSMutableDictionary * dictionary = [NSMutableDictionary dictionaryWithObjects:objects forKeys:keys]; NSEnumerator * enumerator = [keys objectEnumerator]; for (id keys in dictionary) { NSLog(@"key: '%@', value: '%@'", keys, [dictionary objectForKey:keys]); } NSLog(@" "); NSLog(@"These are the ones that has the prefix 'Stanford'."); NSLog(@" "); id object; while (object = [enumerator nextObject]) { if ([object hasPrefix: @"Stanford"]) { NSLog(@"key: '%@', value: '%@'", object, [dictionary objectForKey:object]); } } NSLog(@"--------------------"); NSLog(@"\n"); } void PrintIntrospectionInfo() { NSLog(@"Section 4"); NSLog(@"--------------------"); SEL lowercase = @selector (lowercaseString); NSMutableArray * array = [NSMutableArray array]; [array addObject: [NSString stringWithString: @"Here is a string"]]; [array addObject: [NSDictionary dictionary]]; [array addObject: [NSURL URLWithString: @"http://www.stanford.edu"]]; [array addObject: [[NSProcessInfo processInfo]processName]]; for (id keys in array) { NSLog(@"\n"); NSLog(@"Class Name: %@", [keys className]); NSLog(@"Is Member of NSString: %@", [keys isMemberOfClass:[NSString class]]?@"Yes":@"No"); NSLog(@"Is Kind of NSString: %@", [keys isKindOfClass:[NSString class]]?@"Yes":@"No"); if ([keys respondsToSelector: lowercase]==YES) { NSLog(@"Responds to lowercaseString: %@",[keys respondsToSelector: lowercase]?@"Yes":@"No"); NSLog(@"lowercaseString is: %@", [keys performSelector: lowercase]); } else { NSLog(@"Responds to lowercaseString: %@",[keys respondsToSelector: lowercase]?@"Yes":@"No" ); } } NSLog(@"--------------------"); } void PrintPolygonInfo() { NSMutableArray * array = [NSMutableArray array]; PolygonShape * polygon1 = [[PolygonShape alloc]initWithNumberOfSides:4 minimumNumberOfSides:3 maximumNumberOfSides:7]; [array addObject:polygon1]; [array description]; PolygonShape * polygon2 = [[PolygonShape alloc]initWithNumberOfSides:6 minimumNumberOfSides:5 maximumNumberOfSides:9]; [array addObject:polygon2]; [array description]; PolygonShape * polygon3 = [[PolygonShape alloc]initWithNumberOfSides:12 minimumNumberOfSides:9 maximumNumberOfSides:12]; [array addObject:polygon3]; [array description]; [array release]; [polygon1 release]; [polygon2 release]; [polygon3 release]; } int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; PrintPathInfo(); PrintProcessInfo(); PrintBookmarkInfo(); PrintIntrospectionInfo(); PrintPolygonInfo(); [pool release]; return 0; } //The result was "EXC_BAD_ACCESS", but I couldn't figure out how to resolve this problem.

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  • Memory management of objects returned by methods (iOS / Objective-C)

    - by iOSNewb
    I am learning Objective-C and iOS programming through the terrific iTunesU course posted by Stanford (http://www.stanford.edu/class/cs193p/cgi-bin/drupal/) Assignment 2 is to create a calculator with variable buttons. The chain of commands (e.g. 3+x-y) is stored in a NSMutableArray as "anExpression", and then we sub in random values for x and y based on an NSDictionary to get a solution. This part of the assignment is tripping me up: The final two [methods] “convert” anExpression to/from a property list: + (id)propertyListForExpression:(id)anExpression; + (id)expressionForPropertyList:(id)propertyList; You’ll remember from lecture that a property list is just any combination of NSArray, NSDictionary, NSString, NSNumber, etc., so why do we even need this method since anExpression is already a property list? (Since the expressions we build are NSMutableArrays that contain only NSString and NSNumber objects, they are, indeed, already property lists.) Well, because the caller of our API has no idea that anExpression is a property list. That’s an internal implementation detail we have chosen not to expose to callers. Even so, you may think, the implementation of these two methods is easy because anExpression is already a property list so we can just return the argument right back, right? Well, yes and no. The memory management on this one is a bit tricky. We’ll leave it up to you to figure out. Give it your best shot. Obviously, I am missing something with respect to memory management because I don't see why I can't just return the passed arguments right back. Thanks in advance for any answers!

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  • Please help with iPhone Memory & Images, memory usage crashing app

    - by Andrew Gray
    I have an issue with memory usage relating to images and I've searched the docs and watched the videos from cs193p and the iphone dev site on memory mgmt and performance. I've searched online and posted on forums, but I still can't figure it out. The app uses core data and simply lets the user associate text with a picture and stores the list of items in a table view that lets you add and delete items. Clicking on a row shows the image and related text. that's it. Everything runs fine on the simulator and on the device as well. I ran the analyzer and it looked good, so i then starting looking at performance. I ran leaks and everything looked good. My issue is when running Object Allocations as every time i select a row and the view with the image is shown, the live bytes jumps up a few MB and never goes down and my app eventually crashes due to memory usage. Sorting the live bytes column, i see 2 2.72MB mallocs (5.45Mb total), 14 CFDatas (3.58MB total), 1 2.74MB malloc and everything else is real small. the problem is all the related info in instruments is really technical and all the problem solving examples i've seen are just missing a release and nothing complicated. Instruments shows Core Data as the responsible library for all but one (libsqlite3.dylib the other) with [NSSQLCore _prepareResultsFromResultSet:usingFetchPlan:withMatchingRows:] as the caller for all but one (fetchResultSetReallocCurrentRow the other) and im just not sure how to track down what the problem is. i've looked at the stack traces and opened the last instance of my code and found 2 culprits (below). I havent been able to get any responses at all on this, so if anyone has any tips or pointers, I'd really appreciate it!!!! //this is from view controller that shows the title and image - (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; self.title = item.title; self.itemTitleTextField.text = item.title; if ([item.notes length] == 0) { self.itemNotesTextView.hidden = YES; } else { self.itemNotesTextView.text = item.notes; } //this is the line instruments points to UIImage *image = item.photo.image; itemPhoto.image = image; } - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { // Delete the managed object for the given index path NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; [context deleteObject:[fetchedResultsController objectAtIndexPath:indexPath]]; // Save the context. NSError *error = nil; if (![context save:&error]) //this is the line instruments points to { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); exit(-1); } } }

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