Hi i am new to iphone development,can any one help how to append string to mutable string.
im trying to string By appending String Format .application Is crashes...
Sample code NSMutableString:
NSMutableString* mutString = [[NSMutableString alloc] init];
for(int index=0;index<10;index++)
{
[mutString appendString:[NSString stringWithFormat:#"%d",index]];
}
NSLog(#"Content in MutableString: %#",mutString);
Regarding crash: post your code that crashes. What does it say ?
There is a crash when you try to append nil to a NSMutableString - check that.
Also while it does not crash during append - if your NSMutablestring is not initialized - then nothing works and your app might crash later in the code because there is nothing in your string.
Post the crash report, I am sure it will tell you what is going wrong.
Related
I am hacking my way through Swift. I love it but I find myself thinking a few things may be too simple and I question if it's correct.
I am converting a project from Objective-C. In the project I have a string property that is use in a method. In Objective-C I did the following to initialize and allocate the object. Once it's initialized and allocated I set it to an empty string.
NSMutableString *tempString = [[NSMutableString alloc] init];
self.currentParsedCharacterData = tempString;
[currentParsedCharacterData setString: #""];
In Swift I typed the following. Is it really this easy or am I missing something?
self.currentParsedCharacterData = ""
I find myself wanting to do the following but I'm not sure it's necessary.
var tempString : String = ""
self.currentParsedCharacterData = tempString
Take care,
Jon
Yes, its this easy. In Objective-C, you could have typed self.currentParsedCharacterData = #"".mutableCopy and achieved the same effect.
#"" in Objective-C and "" in Swift are object literals that allocate memory and initialise for you. Equally for arrays, you can do #[] for an empty NSArray or [] for an empty Array (in Swift) to allocate and initialise an empty array.
I have built one 'deep' NSMutableDictionary that contains parsed XML data along with other relevant information that I can pass from one view controller to another. The NSMutableDictionary contains mostly NSStrings but also another NSMutableDictionary more NSStrings and finally followed even deeper with an NSMutableArray of custom objects (it's for a calendar).
Now, because it is a calendar, there are obviously dates involved. The XML data that I receive and parse using NSXMLParser returns strings, so it was on me to convert the day's date to usable numbers. The date in XML comes in with the following format: "MM.DD" I created the following method to do so:
- (void)createDateCodesWithString:(NSString *)string
{
NSInteger monthCode;
NSInteger dayCode;
....
NSArray *dates = [string componentsSeparatedByString:#"."];
monthCode = [[dates objectAtIndex:0] integerValue];
dayCode = [[dates objectAtIndex:1] integerValue];
....
shortDay = [NSNumber numberWithInt:dayCode];
}
'shortDay' is a NSNumber* and an ivar and set as a property (nonatomic, retain) for the custom object that I have created. When I run NSLog commands in the console, it appears that 'shortDay' and other data has been stored successfully in the deep NSMutableDictionary. I run in to problems, however, when I try to access the data again. When I access a NSString* stored ivar, things work OK, but when I attempt to access the NSNumber* I am given the error EXC_BAD_ACCESS with either code 1 or code 2. This is how I try to call upon the NSNumber*
NSNumber *number = day.shortDay;
return [number stringValue];
Might the problem be because the NSArray *dates strips the string into month and day strings and the day string, being two characters long, may contain a '0' before, say, a '6' if the day is the 6th of the month? Any advice?
I am happy to post more code if needed.
It's possible that the memory for shortDay is being cleaned up before the next time you try to access it. When assigning it, try this instead:
shortDay = [[NSNumber numberWithInt:dayCode] retain];
to increase the reference count (AKA take ownership of the object) to avoid the memory being deallocated too early.
If this resolves the problem, you will then need to call [shortDay release] in the dealloc method of your class, such that the memory for it will be properly deallocated at the right time.
When I construct a dynamic URL using NSString stringWithFormat and then use that value in my XML parser I get random crashes. However if I test it with a constant string it works fine...
This is my code for generating the string,
loginURL = [NSString stringWithFormat:#"%#%#",ScriptURLString,#"authenticate"];
Which results in,
http://edms.digistorm.com.au/test/index.php?s=&sc=D41D8CD98F00B204E9800998ECF8427E&m=authenticate
Then I use it in my XML parser,
XMLReturnData = [[NSMutableArray alloc] init];
xml = [[XMLParser alloc]
initWithXMLPath:loginURL
lookForElement:#"Authenticate"
setCallbackObject:self
withSelector:#selector(dataReady)
data:XMLReturnData
];
For some reason this is causing my app to crash. If I use a constant string like,
loginURL = #"http://edms.digistorm.com.au/test/index.php?s=&sc=D41D8CD98F00B204E9800998ECF8427E&m=authenticate";
it works fine...
loginURL is defined as NSString *loginURL; inside my header file for this view.
Any help or guidance would be much appreciated!
Thanks,
Tim
The method you are using to allocate the string is important.
You have two basic ways to allocate your string:
NSString *loginURL = [[NSString alloc] initWithFormat:#"%#authenticate", ScriptURLString];
Compared to:
NSString *loginURL = [NSString stringWithFormat:#"%#authenticate", ScriptURLString];
For the first, Cocoa conventions say that because you caused the object to be created via an alloc message you "own" it and are responsible for releasing it.
For the latter, the convention is that because you caused the object to be created by a class "convenience" method, you do NOT own it and are not responsible for releasing it. The class (here, NSString) has that responsibility which it will discharge through an autorelease pool.
To summarise, when you explicitly create something with an alloc/init, you must release it. When you use a [NSThing thingWithXXX] style method you must not.
This shows your string is get released and when you calls it in XML parser it crashes the app.
actually stringWithFormat gives a autorelease object for string.
So what you need,make your string as retain property inside .h then synthesize it in .m and release it in dealloc method.
and also do this,
in viewDidLoad
NSString *tempString=[[NSString alloc] init]; //using this because your string is retain type so it prevent increment in retain count.
self.loginURL=tempString;
[tempString release];
Now when you use stringWithFormat use like this
self.loginURL = [[NSString stringWithFormat:#"%#%#",ScriptURLString,#"authenticate"] retain];
It solves your problem.
Not to call release on loginURL, because you have'nt alloced it and only iOS have right to destroy it...
Use below code
loginURL = [[NSString alloc] initWithFormat:#"%#%#",ScriptURLString,#"authenticate"];
Once you used loginURL Do'nt forget to call release on it ...
[loginURL release];
Try this, it might help you.
loginURL = [NSString stringWithFormat:#"%#authenticate",ScriptURLString];
I'm getting a potentially leaked object error from the Static Analyzer for this line:
strCleanPhone = [[[[strPhone stringByReplacingOccurrencesOfString:#" " withString:#""]
stringByReplacingOccurrencesOfString:#"(" withString:#""]
stringByReplacingOccurrencesOfString:#")" withString:#""]
stringByReplacingOccurrencesOfString:#"-" withString:#""];
For one, is this the preferred way to strip non-numeric characters from a phone number string?
Two, can you possibly explain why this would be a leaked object?
The strings created by stringByReplacingOccurrencesOfString are autoreleased, so they aren't leaked. If there's a leak, it has to do with strPhone and strCleanPhone.
For example, if strCleanPhone is a #property with the retain option, and is currently not nil, then your code leaks it. To use the release/retain code that was generated by synthesize you have to use the property syntax: self.strCleanPhone = .... Using just strCleanPhone = ... sets the instance variable and doesn't release any object it was pointing to.
If you're on iOS 4.0+, you might be able to use the new NSRegularExpression object to do this a little more elegantly.
The code you have as posted doesn't leak. It just creates four autoreleased string objects.
If you are looking to strip out characters that are not numbers.
NSString *strPhone = #"(555) 444-3333";
NSMutableString *strCleanPhone = [NSMutableString string];
for (int i=0;i<[str length];i++)
{
unichar ch = [str characterAtIndex:i];
if (isnumber(ch)) [strCleanPhone appendFormat:#"%c", ch];
}
But I suggest looking into regular expressions.
Make sure you expand the analyzer warning by clicking the warning text in the source view! Chances are it's pointing to where a variable is last referenced; if you expand the warning you'll see a bunch of arrows indicating code flow, which will help indicate where you've allocated your potentially-leaked object.
(tl;dr: Post more code.)
I'm trying to swap two strings but I'm not sure if what I am doing is legal (coming from java I'm new to the whole retain count memory management).
Here's my code:
NSString *temp = [[NSString alloc] init];
temp = originalLanguageCode;
originalLanguageCode = translatedLanguageCode;
translatedLanguageCode = temp;
[temp release];
Is this allowed? I'm getting some strange bugs and I'm not sure what's causing them, hoping that this might be it. Any help is very appreciated, thanks!
After assigning a newly allocated string to temp you are immediately assigning originalLanguageCode to it, so the allocated string is completely lost. That is a memory leak. Then you are releasing temp, which was originally originalLanguageCode. This is an over-release.
Try this instead:
NSString *temp = originalLanguageCode;
originalLanguageCode = translatedLanguageCode;
translatedLanguageCode = temp;
Everything looks fine except that in your first line you're creating a string which you immediately leak on the second. You can just say:
NSString *temp = originalLanguageCode;
...
... and get rid of the [temp release] since you didn't create (and don't own) the object assigned to "temp."
Now you didn't say whether originalLanguageCode and translatedLanguageCode are instance variables. If so, use their accessors (which should themselves be doing the right thing with memory management).