I declare a variable in the header file and synthesize it in the implementation. When the view loads (ViewDidLoad) I read a plist file an populate the variable with a value. WIth my NSLog I see that the variable contains the value. However, after the view loads, I have some interaction with the user via a button the executes a method. WIthin that method I check the value again and it is invalid. Why won't the variable maintain its value after the initial load?
program.h
....
NSString * user_title;
...
#property (nonatomic, retain) NSString *user_title;
program.m
#synthesize user_title;
-(void)viewDidLoad{
NSString *filePath = [self dataFilePath];
if ([[NSFileManager defaultManager] fileExistsAtPath:filePath])
{
NSArray *array = [[NSArray alloc] initWithContentsOfFile:filePath];
user_title = [array objectAtIndex:0];
[array release];
}
....
-(IBAction)user_touch_screen:(id)sender
{
user_label.text = user_title; //user_title has an invaliud value at this point
....
user_title = [array objectAtIndex:0] doesn't retain the variable.
Use this instead:
self.user_title = [array objectAtIndex:0];
That will use the setter that you synthesized, and will retain the value.
You need to retain the value you get out of the array.
Related
In one of my methods, I fetched and parsed a JSON and placed it inside an NSArray called jsonArray in -(void)method1. I then copied the contents of that jsonArray to an NSMutableArray called copiedJsonArray to be used on other methods. Problem is, copiedJsonArray crashes whenever I log its contents in the console from the other methods -(void)method2 but it logs fine in -(void)method1.
How can I fix this?
In my header file:
#interface MainViewController : UIViewController
#property (nonatomic, retain) NSMutableArray *copiedJsonArray;
In my implementation file:
#synthesize copiedJsonArray;
- (void)viewDidLoad
{
[self method1];
}
- (void)method1
{
NSString *urlString = [NSString stringWithFormat:THE_URL];
NSURL *url = [NSURL URLWithString:urlString];
NSData *data = [NSData dataWithContentsOfURL:url];
NSString *jsonString = [[[NSString alloc] initWithData:data
encoding:NSUTF8StringEncoding] autorelease];
NSDictionary *jsonDictonary = [jsonString JSONValue];
NSArray *jsonArray = [jsonDictonary valueForKeyPath:#"QUERY.DATA"];
self.copiedJsonArray = [[NSMutableArray alloc] initWithArray:jsonArray copyItems:YES];
NSLog(#"Copied JSON Array in Method 1: %#", self.copiedJsonArray);
[self method2];
}
- (void)method2
{
NSLog(#"Copied JSON Array in Method 2: %#", self.copiedJsonArray);
}
I also tried doing this too but it does the same error:
copiedJsonArray = [jsonArray mutableCopy];
I also tried implementing NSCopy but fails too:
#interface MainViewController : UIViewController <NSCopying>
{
NSMutableArray *copiedJsonArray;
}
I'm doing this so that I can do a loop in my copiedJsonArray without fetching its contents from JSON again and again when the user taps on my UISegmentedControl.
If you call method2 before method1 it will crash as copiedJasonArray has not been created. You should not create instance variables inside methods (as you cannot know if they have been called). You should do it when you create your viewController, in viewDidLoad for example.
And use properties:
#interface
#property (retain) NSMutableArray* copiedJsonArray;
#end
then either
#synthesize copiedJsonArray = _copiedJsonArray
or leave that line it out (the compiler will put it in automatically in 4.5)
access as self.copiedJsonArray or _copiedJSONArray.
Outside of getters,setters,inits and deallocs, use the self. form, it's safer.
You could also create _copiedJsonArray lazily in the setter:
- (NSMutableArray*) copiedJsonArray
{
if (!_copiedJasonArray)
_copiedJsonArray = [NSMutableArray alloc] init;
return _copiedJasonArray;
}
I use "EasyTableView" which is an extend UITableView. I encounter a problem as below:
- (void)viewDidLoad
{
NSArray *array = [[NSArray alloc] initWithObjects:#"14.jpg",nil];
photos = array;
[array release];
[photos objectAtIndex:0]; //this "photos" can be access
}
but when i try to access the "photos" in the delegate method:
- (void)easyTableView:(EasyTableView *)easyTableView setDataForView:(UIView *)view forIndexPath:(NSIndexPath *)indexPath {
NSInteger r = [indexPath row]; // r = 0
NSString *imagePath = [photos objectAtIndex:r]; //this line cause : reason: '-[CALayer objectAtIndex:]: unrecognized selector sent to instance
}
Why the result to access photos is different? How can i fix it?
use photos as property as
#property (nonatomic, retain) NSMutableArray* photos;
and in implementation
#synthesize photos = photos;
it will be accessible in delegate now
The photos variable isn't retaining the array you assign to it. When it is deallocated, the memory is being re-used to point to a CALayer object. If photos is a retained property, you should use self.photos = array; to make the assignment. If it's just a simple variable, then allocate it directly instead of using array.
I have no idea where this code is wrong. Please help, it is supposed to read a value from a dictionary and I use the value to call an image. I've tried to read the value as label.text but I got no result.
The only one I can call is from the nslog.
for (id key1 in dictionary)
{
NSMutableString *textnamed = [dictionary objectForKey:key1];
NSMutableString *imageDisplay =[NSMutableString stringWithFormat:#"%#.png",[dictionary objectForKey:key1]];
eyeImageSaved.image = [UIImage imageNamed:imageDisplay];
labelSaved.text = textnamed;
NSLog(#"%#",textnamed);
}
There are a few issues with your code. First of all, you should consider using NSString instead of NSMutableString because it should be faster. Second, why are you putting the dictionary object in a string then calling the dictionary object again in the next line? That first line is unnecessary. It's entirely possible that the dictionary entry is not a string, and that is why you are having issues. You should write it like this NSString *textnamed = (NSString *)[dictionary objectForKey:key1]. Also, imageNamed can only be used for files in the file bundle. Are you sure those pictures are stored there? There are a few other issues you could be having. What exactly is going wrong here?
I solved my problem. There is nothing wrong with my code above, the mistake I made is that the object that is supposed to hold my variable and store in plist as the name of the image became null. So I added the object to appdelegate.h as seen below:
AppDelegate
#interface AppDelegate : UIResponder <UIApplicationDelegate>
{
NSString *imageNameHolder;
}
#property (retain, nonatomic) NSString *StorageDecider;
View Controller
- (IBAction)lips2:(id)sender {
imageNameHolder = #"lips_blue";
}
-(void)writeNewPlist
{
AppDelegate* ref = (AppDelegate*) [[UIApplication sharedApplication] delegate];
[dictionary setObject:imageNameHolder forKey:#"image1"];
[dictionary writeToFile:finalPath atomically:YES];
}
nameDataFormArray_ & imageDataFormArray_ are NSMutableArray. Both have string and find image as per string (name of image).
- (void)readInfoFromThePlist
{
NSString* PListPath=[[NSBundle mainBundle] pathForResource:#"dataList" ofType:#"plist"];
NSMutableArray* tempDataList=[[NSMutableArray alloc ] initWithContentsOfFile:PListPath];
for(NSDictionary *dataDict in tempDataList)
{
[nameDataFormArray_ addObject:[dataDict objectForKey:#"name"]];
[imageDataFormArray_ addObject:[dataDict objectForKey:#"imagepath"]];
}
[tempDataList release];
}
I'm new to iPhone development and have had great success with with answers from here so I am hoping to receive help directly. I am reading data into a tableview from a plist. The application works fine but I get 2 warnings when I compile. I know why I get the errors but I have been unsuccessful with resolving the issues. Although this app works I really would like to resolve the warnings efficiently. When I tried changing the NSDictionary to NSArray the warning goes away but the table is no longer populated.
Any help would be greatly appreciated.
Staff and Data are defined as NSArray in the Delegate .h file. The warnings show in the delegate .m file below.
My Delegate has the following:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Override point for customization after application launch.
// Add the tab bar controller's current view as a subview of the window
NSString *Path = [[NSBundle mainBundle] bundlePath];
NSString *DataPath = [Path stringByAppendingPathComponent:#"Data.plist"];
NSString *SPath = [[NSBundle mainBundle] bundlePath];
NSString *StaffPath = [SPath stringByAppendingPathComponent:#"Staff.plist"];
NSDictionary *tempDict = [[NSDictionary alloc] initWithContentsOfFile:DataPath];
**self.data = tempDict;**
[tempDict release];
NSDictionary *staffDict = [[NSDictionary alloc]initWithContentsOfFile:StaffPath];
**self.staff = staffDict;**
[staffDict release];
In my staff ViewController I have the following:
if(CurrentLevel == 0) {
//Initialize our table data source
NSArray *staffDict = [[NSArray alloc] init];
self.tableDataSource = staffDict;
[staffDict release];
Midwest_DigestiveAppDelegate *AppDelegate = (Midwest_DigestiveAppDelegate *)[[UIApplication sharedApplication] delegate];
self.tableDataSource = [AppDelegate.staff valueForKey:#"Rows"];
}
else
self.navigationItem.title = CurrentTitle;
An NSArray holds a one dimensional list of items where an NSDictionary maps keys to values.
Array:
[a, b, c]
Dictionary:
{#"a" = #"first item", #"b" = #"second item"}
Could you declare data as NSDictionary *data; and populate it as data = [[NSDictionary alloc] initWithContentsOfFile:DataPath];
You then access values in the dictionary with [data valueForKey:#"key"]
Everything in your code suggests that the staff and data properties are NSDictionary instances. You initialize them to dictionary objects and you reference them as dictionary objects. Why then are you declaring them as NSArray objects?
You should change how they are declared so they are NSDictionary in your header file rather than NSArray. That seems to me the most logical way to remove your warnings.
This should still work assuming the contents of your "staff" NSDictionary has a key named "Rows" whose value is an NSArray. The code you have to initialize self.tableDataSource with an empty NSArray seems redundant, as you immediately overwrite the value with the
self.tableDataSource = [AppDelegate.staff valueForKey:#"Rows"];
line in your code
in the following piece of code I got from a book.
The NSString *pPath which is defined in the class as an instance variable.
#interface MainViewController : UIViewController {
NSString *pPath;
}
In the implementation after being set it is being retained. I assume that with the assignment the object is automatically retained (because it is an NSString) and there is no need to additionally retain it.
- (void) initPrefsFilePath {
NSString *documentsDirectory =
[NSHomeDirectory() stringByAppendingPathComponent:#"Documents"];
pPath = [documentsDirectory stringByAppendingPathComponent:
#"flippingprefs.plist"];
[pPath retain];
}
Yes, you need to retain your pPath variable if you obtain it this way. However it is not the end of the story - you also need to release its previous value otherwise it will just leak.
To make things easier you can use objective-c properties that allow you to automatically generate setter/getter methods with desired memory management behavior:
// header
#interface MainViewController : UIViewController {
NSString *pPath;
}
#property (nonatomic, retain) NSString* pPath;
// implementation
#synthesize pPath;
- (void) initPrefsFilePath {
NSString *documentsDirectory =
[NSHomeDirectory() stringByAppendingPathComponent:#"Documents"];
self.pPath = [documentsDirectory stringByAppendingPathComponent:
#"flippingprefs.plist"];
}
Here in self.pPath=... line automatically generated setter method will get called which:
Will release previously set pPath value
Will assign new value to pPath and retain it
You will also need to release your pPath variable in dealloc method:
-(void) dealloc{
[pPath release];
//or
self.pPath = nil;
[super dealloc];
}