I'm making an ipad web browser where of course I have an history. The UITableView works well, what doesn't work is the method to add new strings at the history array, and it doesn't give to me any error.
Here's the code:
.h
NSMutableArray *HistoryArray;
.m
-(void)viewDidLoad{
HistoryArray = [[NSMutableArray alloc]init];
}
-(void) addStringsToTheHistory{
NSString *firstURL;
[firstURL isEqual: #"http://www.google.com"];
NSString *currentURL;
[currentURL isEqual: field.text];
[HistoryArray addObject: #"http://www.google.com"];
if ([firstURL isEqual: currentURL]) {
[firstURL isEqual: #"something"];
[TableView reloadData];
}else{
[HistoryArray addObject: currentURL ];
[TableView reloadData];
}
}
Anyone has any idea why it doesn't work well? Is it something about how the HistoryArray is initiated?
The isEqual: method is an object equivalence test and returns a BOOL value. The lines:
NSString *firstURL;
[firstURL isEqual: #"http://www.google.com"];
NSString *currentURL;
[currentURL isEqual: field.text];
don't actually set the variables firstURL and currentURL to anything.
If you want to test for equality between two strings you should use:
if ([firstURL isEqualToString:currentURL]) {
}
If you still don't get the result you expect - set breakpoints or use NSLog functions to inspect the contents of your variables in your viewDidLoad and addStringsToHistory methods.
Related
I'm trying to sort an array, filled with objects from a class i wrote. The class i wrote contains an NSString itself, as the "name". So what i wanna do, is to sort the array, based on the name property the objects contain. I tried the simple:
[anArray sortedArrayUsingSelecter: CaseInsensitiveCompare];
But as you can guess, it sends the caseInsensitiveCompare message to the objects itself, and it won't respond to that one.
So i'm guessing i have to make my objects able to respond to the caseInsensitiveCompare? Not quite sure how to write such a method, so any pointers would be lovely.
Thanks
You can use the method sortedArrayUsingComparator:
NSArray *sortedArray = [anArray sortedArrayUsingComparator:^(MyClass *a, MyClass *b) {
return [a.name caseInsensitiveCompare:b.name];
}];
You can sortedArrayUsingComparator:(NSComparator)cmptr (NSArray reference) to sort the array. For instance, if you want to sort by the name property, do the following (assuming your class is called Person):
NSArray *sortedArray = [anArray sortedArrayUsingComparator:^(id a, id b) {
NSString *first = [(Person *)a name];
NSString *second = [(Person *)b name];
return [first caseInsensitiveCompare:second];
}];
I have a signature page, were the user can sign their name.
It needs to then be saved to NSDictionary, but i want to call a List of the keys to be text in a TableView for each row or cell.
so:
"viewImage = saved as object to key:Random Number"
That parts somewhat easy, the hard part is when i call it on the other Page to the TableView.
It Exits the App with Error"SIGABRT". Now all my Delegates are in place and working...i believe.
now heres some example code:
FirstPage.m
UIImagePNGRepresentation(viewImage);
NSMutableArray *innerArray = [[NSMutableArray array]init];
[innerArray addObject:viewImage];
[SignatureSave setObject:innerArray forKey:#"5599"];
simple Enough, but doesnt give me an error.
SecondPage.m
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
FirstPage *appShare = (FirstPage *)[[UIApplication sharedApplication] delegate];
NSArray *dataDuplicate = [[NSArray alloc]init ];
dataDuplicate = [appShare.SignatureSave allKeysForObject:#"innerArray"];
static NSString *CellIdentifier = #"Cell";
NSLog(#"%#",dataDuplicate);
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if(cell == nil)
{
cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero]autorelease];
}
if (dataDuplicate != nil) {
cell.textLabel.text = [dataDuplicate objectAtIndex:indexPath.row];
}
else
{
UIAlertView *CellAlert = [[UIAlertView alloc] initWithTitle:#"Error" message:#"Error Loading content, Try Again Later." delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil];
[CellAlert show];
[CellAlert release];
}
return cell;
}
#end
Now, How do i get the viewImage to save to the NSDictionary, to be able to call it on the SecondPage and display the name of the objects in the TableVIew?
I really don't understand whats your problem exactly.
first of all, is your dictionary a retained object?
//FirstPage.h
#property (nonatomic, retain) NSDictionary *SignatureSave;
//FirstPage.m
#synthesize SignatureSave;
…
UIImagePNGRepresentation(viewImage);
NSMutableArray *innerArray = [NSMutableArray array]; // using "array" is equivalent to alloc-init-autorelease
[innerArray addObject:viewImage];
[self.SignatureSave setObject:innerArray forKey:#"5599"];
// OR setting the array directly:
UIImagePNGRepresentation(viewImage);
NSArray *innerArray = [NSArray arrayWithObject:viewImage];
[self.SignatureSave setObject:innerArray forKey:#"5599"];
// OR even setting the image directly to the dictionary:
UIImagePNGRepresentation(viewImage);
[self.SignatureSave setObject:viewImage forKey:#"5599"];
now if you access the object by writing self. in front it will call the retain and your object will stay alive. Otherwise it would be autoreleased at the end of the method. This will fix the problem that your dictionary is maybe not present/available at table view creation and you don't have to use a singleton.
what are you trying to access with this code?
FirstPage *appShare = (FirstPage *)[[UIApplication sharedApplication] delegate];
with [[UIApplication sharedApplication] delegate] you get your application delegate (obviously). These are the MyAppNameAppDelegate files but you treat it as a FirstPage class.
Just NSLog() to check you get the right class, the one you expect.
NSLog(#"%#", [[[UIApplication sharedApplication] delegate] class]);
here you have a potential leak, you alloc-init but never release it:
NSArray *dataDuplicate = [[NSArray alloc]init ];
dataDuplicate = [appShare.SignatureSave allKeysForObject:#"innerArray"];
furthermore you can simplify it (will be autoreleased):
NSArray *dataDuplicate = [appShare.SignatureSave allKeysForObject:#"innerArray"];
and here you have another issue.
Why do you call all keys for the object #"innerArray"?
you don't have such an object and it's in many more cases wrong. innerArray was your previously named array in FirstPage.m but it is only for you as a developer to remember the variable better. After compilation it will have a cryptic name anyway. You could access your key #"5599" if you like but I don't think you want this. In your case you want to access all keys of the dictionary so simply call:
NSArray *dataDuplicate = [appShare.SignatureSave allKeys];
now you will have an array with all keys of your dictionary and you can access them like you do with objectAtIndex:.
NSString *keyName = [dataDuplicate objectAtIndex:indexPath.row];
cell.textLabel.text = keyName;
id theObject = [appShare.SignatureSave objectForKey:keyName]; // for example the image
Tell me if this solves your problems or tell me how I misunderstood your question.
I found the answer to this to be quit simple actually,
I ended up going with the Singleton Method instead of the Global Variable Method.
Now the Singleton Method looks terrifying but its quit simple, See here.
The main difference i noticed from the singleton method to the global method is,
Global method takes a lot of converting and re-converting.
Though the Singleton Method is working with a single object over many pages or classes.
Now i hope this will better assist people in the future also!
When inserting an object into an array with a property is there any reason to invoke the getter/setter with self? i.e.
[self.myArray insertObject: myObject];
Or can I just use:
[myArray insertObject: myObject];
the gist would be:
.h
#interface ArrayViewController : UIViewController <UITextFieldDelegate>
{
NSMutableArray *myArray;
int itemNumber;
}
#property (nonatomic, retain) NSMutableArray *myArray;
#end
.m
- (IBAction)createMyArray
{
self.myArray = [[NSMutableArray alloc] initWithObjects: nil];
}
-(IBAction) addItemToMyArray
{
NSString *myString = [[NSString alloc] initWithFormat:#"item %d",itemNumber];
[myArray addObject: myString];
//[self.myArray addObject: myString]; //Or should I use self?
[myString release];
NSLog(#"myArray = %#", myArray);
itemNumber++;
}
//- (void)dealloc etc. not shown
Conceptually, it doesn't matter, so long as your getter method only returns the existing field value and doesn't, eg, do some "just in time" allocation or some such.
However, it's good practice to come up with a policy (personal or group) that you stick with, so that the caveats of that policy become second nature. Constantly switching styles results in sloppy, buggy code.
I tend to always use the self. for properties, just to remind myself that they are, in fact, properties, and to make it less likely that I'll accidentally set the value without using the property notation.
Either will work but you need to be aware of what you are doing. Using self. will invoke the setter/getter methods while the other will just access the variable directly. Using the variable directly, while perfectly valid, is discouraged outside of the initializer and dealloc method. The reason is you are losing out on the benefits of the property, especially setting using self. because it will properly assign/copy/retain the value for you correctly. Another reason not use property variables directly is because of atomicity but in your case you declared it as nonatomic.
Both of those are fine. It's mostly a stylistic choice. Using self.myArray will result in a call to the getter [self myArray].
When using alloc/init you should not set the returned value to a property, as these will retain twice:
self.myArray = [[NSMutableArray alloc] initWithObjects: nil];
use
myArray = [[NSMutableArray alloc] initWithObjects: nil];
or
self.myArray = [NSMutableArray array];
for the initialization.
The insert operations are equivalent though.
I typically skip the getter because I rarely find it valuable and it clutters up the readability of the code a bit. However, I tend to use the setter because I find it easier to allow the auto-generated setter methods to handle the retain/release semantics
In your case it's not an obligation to use self.myArray but for this case belloaw it will be an obligation:
-(void) addItemToMyArray:(NSAarray *)myArray
{
NSString *myString = [[NSString alloc] initWithFormat:#"item %d",itemNumber];
[self.myArray addObject: myString];
[myString release];
NSLog(#"myArray = %#", self.myArray);
itemNumber++;
}
to difference between the class attribut and the function argument.
I've created a small class that loads dictionary items from a plist file. The getSettingForKey method works the first time I call the static method, however after a few more calls the dictionary throws a SIGABRT exception for a call with the same key that worked on a previous call. Any ideas?
static NSDictionary *dictionary = nil;
static NSLock *dictionaryLock;
#implementation ApplicationSettingsHelper
+ (void) initialize
{
dictionaryLock = [[NSLock alloc] init];
// Read plist from application bundle.
NSString *path = [[NSBundle mainBundle] bundlePath];
NSString *finalPath = [path stringByAppendingPathComponent:#"Xxxx.plist"];
dictionary = [NSDictionary dictionaryWithContentsOfFile:finalPath];
// dump the contents of the dictionary to the console.
for(id key in dictionary)
{
NSLog(#"bundle: key=%#, value=%#", key, [dictionary objectForKey:key]);
}
}
+ (NSDictionary *)dictionaryItems
{
[dictionaryLock lock];
if (dictionary == nil)
{
[self initialize];
}
[dictionaryLock unlock];
return dictionary;
}
+(id)getSettingForKey:(NSString *)key
{
return [[self dictionaryItems] objectForKey:key];
}
#end
Moshe - I've taken your suggestion and updated to use NSUserDefaults instead:
+ (void)load
{
// Load the default values for the user defaults
NSString* pathToUserDefaultsValues = [[NSBundle mainBundle]
pathForResource:#"Xxxx"
ofType:#"plist"];
NSDictionary* userDefaultsValues = [NSDictionary dictionaryWithContentsOfFile:pathToUserDefaultsValues];
// Set them in the standard user defaults
[[NSUserDefaults standardUserDefaults] registerDefaults:userDefaultsValues];
}
+ (id)getSettingForKey:(NSString *)key
{
return [[NSUserDefaults standardUserDefaults] valueForKey:key];
}
Your dictionary has probably been deallocated, causing an invalid memory access. When you create a dictionary using the dictionaryWithContentsOfFile: method, it is autoreleased, which means it will automatically be released in the future. Since you never retain the dictionary, that release will cause the dictionary to be deallocated.
Also, most of your dictionaryItems method is useless.
[dictionaryLock lock];
if (dictionary == nil) {
[self initialize];
}
[dictionaryLock unlock];
The +initialize method is automatically called by the runtime before any other method is called on your class, unless you have a +load method. Since the runtime will call it for you and it will attempt to create the dictionary, the dictionary can only be nil in the dictionaryItems method if there wasn't enough memory to create it, in which case it will fail again. Also, if you don't use the lock anywhere else, it is unnecessary also, since removing that check would cause it to be locked and immediately unlocked. Therefore, you can remove the lock and change your dictionaryItems method to simply:
+ (NSDictionary *)dictionaryItems {
return dictionary;
}
In addition to #ughoavgfhw's answer, you are also initializing dictionaryLock after you are locking it. Unless you are initializing dictionaryLock somewhere else, I'm surprised your code is getting as far as it is.
Edit: I see from #ughoavgfhw's edit that +initialize is called before anything else, so your lock is initialized there.
i got an NSArray which gets filled in the init Method of my UITableViewController.
i use this object in "didSelectRowAtIndexPath" for pushing another tableviewcontroller.
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
ablogSingleCatTableViewController *singleCatTableViewController = [[ablogSingleCatTableViewController alloc] initWithStyle:UITableViewStylePlain category:[categories objectAtIndex:indexPath.row]];
[[self navigationController] pushViewController:singleCatTableViewController animated:YES];
[singleCatTableViewController release];
}
this works a few times when i start my application. after selecting a row and getting back to the main uitableview controller at a rondom point my application crashes after selecting a row.
with some nslogs i found out, that it crashes if i try to use my "categories" object.
so
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
NSLog(#"before");
NSLog(#"cats: %#", categories);
NSLog(#"after");
ablogSingleCatTableViewController *singleCatTableViewController = [[ablogSingleCatTableViewController alloc] initWithStyle:UITableViewStylePlain category:[categories objectAtIndex:indexPath.row]];
[[self navigationController] pushViewController:singleCatTableViewController animated:YES];
[singleCatTableViewController release];
}
with that code my application crashes after "before" ... "after" never shows up.
i dont know why my "categories" object is crashing my application ?!
my categories object is defined in my header file and has a #property (nonatomic, retain). i synthesize it and releasing it in my dealloc method.
anyone has an idea?
// edit:
some more details here, because of the comments:
Debugger Console says: "Program received signal: “EXC_BAD_ACCESS”.
i create the category array like this:
- (void)initCategories {
NSString *path = [[NSBundle mainBundle] pathForResource:#"Categories" ofType:#"plist"];
[self setCategories:[[NSArray alloc] initWithContentsOfFile:path]];
}
calling this method in my initwithstyle method
[self initCategories];
my other custom initializing method looks something like this:
- (id)initWithStyle:(UITableViewStyle)style category:(NSDictionary*)cat {
if (self = [super initWithStyle:style]) {
currentCategory = cat;
items = [[NSMutableArray alloc] init];
self.title = [currentCategory objectForKey:#"TITLE"];
//XLog("%#", currentCategory);
}
return self;
}
ok, first thing is ;
[self setCategories:[[NSArray alloc] initWithContentsOfFile:path]];
you have a leak here. just use
categories = [[NSArray alloc] initWithContentsOfFile:path];
Crash occurs in here;
currentCategory = cat;
you have to retain, use;
currentCategory = [cat retain];
These are the problems I see in posted code, if you have not any mistake in the rest of the program, it should be fine with these fixes.
If you are creating your array something like this:
NSArray *tmpArray = [[NSArray alloc] initWithBlah ...];
Make sure that you assign it using the synthesized getter by using this code:
self.categories = tmpArray;
[tmpArray release];
If you do:
categories = tmpArray;
[tmpArray release];
the instance variable will not be retained at all.