Recreating NSMutableArray - ios

Question

I have a NSMutableArray called _objects stored in NSUserDefaults. I access _objects upon app launch and put them in a CollectionView with custom cell (see below). I let the user edit each item by first entering edit mode and then tapping the desired cell. The cell class then alters the visual appearance correspondingly and reveal a UITextField. Whenever the user presses done on the keyboard while entering data here, the ProjectsViewController (CollectionView viewcontroller) gets a notification from the custom class to resave the items. How can I save the new _objects then?
Specifically I need to edit a cell (done), edit the corresponding item in _objects and resave _objects. How can I achieve this?
My custom class:
ProjectCell.h:
#import <UIKit/UIKit.h>
#interface ProjectCell : UICollectionViewCell
#property (weak, nonatomic) IBOutlet UILabel *projectLabel;
#property (weak, nonatomic) IBOutlet UILabel *projectCount;
#property (weak, nonatomic) IBOutlet UITextField *projectTextField;
#property (weak, nonatomic) IBOutlet UILabel *editModeLabel;
#property (nonatomic, assign) BOOL editMode;;
-(void)editProject;
#end
ProjectCell.m:
#import "ProjectCell.h"
#import "QuartzCore/CALayer.h"
#implementation ProjectCell
#synthesize editMode;
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
}
return self;
}
-(void)awakeFromNib {
// Custom initial code
[_projectTextField setDelegate:self];
[_projectTextField setReturnKeyType:UIReturnKeyDone];
[_projectTextField addTarget:self
action:#selector(editingFinished:)
forControlEvents:UIControlEventEditingDidEndOnExit];
}
- (IBAction)editingFinished:(id)sender
{
// Update the project cell visually
_projectLabel.text = _projectTextField.text;
// disable editMode and update the project cell
editMode = NO;
_projectTextField.hidden = YES;
_editModeLabel.hidden = YES;
// Reload the MasterViewController
[[NSNotificationCenter defaultCenter] postNotificationName:#"saveNewProjects" object:self];
}
-(void)editProject {
if (editMode == YES) {
// disable editMode and update the project cell
editMode = NO;
_projectTextField.hidden = YES;
_editModeLabel.hidden = YES;
} else if (editMode == NO) {
// Enable editMode and update the project cell
editMode = YES;
_projectTextField.hidden = NO;
_editModeLabel.hidden = NO;
}
}
/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
// Drawing code
}
*/
#end
ProjectsViewController.m
This method is called whenever the user presses "done" while editing a cell.
I tried to cycle through every item and "recreate" the NSMutableArray but I
don't think this is a very good approach.
- (void)resaveProjects:(NSNotification *)notification {
// Edit the edited projects and save all again
editedProjects = editedProjects - 1;
NSMutableArray *newObjects;
int objectsCount = _objects.count;
for (int i = 0; i < objectsCount; i++) {
// Initialize objects
if (!newObjects) {
newObjects = [[NSMutableArray alloc] init];
}
}
}
What do you think is the best approach for this and how do I proceed with that?
Thanks!
Edit:
Reading the _objects:
NSMutableArray *_objects;
_objects = [NSMutableArray arrayWithArray:[[NSUserDefaults standardUserDefaults] objectForKey:#"myProjects"]];

Answer 1

In iOS or Mac OS, when you read a collection object like a dictionary or array (from user defaults or a plist) the object is read in as immutable, even if the original object was mutable.
Thus, after reading in a dictionary from user defaults, you have to convert it to a mutable object.
I would suggest you read your object from user defaults and convert it to a mutable version:
In your header:
#property (nonatomic, strong) NSMutableDictionary *aDict;
And in your .m file, when you read the dictionary:
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSMutableDictionary *aDict = [[defaults objectForKey: #"aDictionaryKey"] mutableCopy];
Then, when the user does something that requires you to change the data:
aDict[key] = newValueFromUser;
[defaults setObject: aDict forKey: #"aDictionaryKey"];
Note that if your dictionary contains other collection objects (arrays or other dictionaries), those also become immutable when read back from a file. That means that you may have to walk through the "object graph" of your dictionary, converting each collection inside to a mutable version and saving it in it's enclosing collection.
I just found some posts online that claim that NSCoding preserves the mutability of objects. If that's the case then you might want to save your dictionary to an archive file rather than saving it to user defaults:
Writing your dictionary to a file:
NSString *documentsDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask, YES) lastObject]
NSString *path = [documentsDir stringByAppendingPathComponent: #"dictFile"];
[NSKeyedArchiver archiveRootObject: myDict toFile: path];
Reading it back:
NSString *documentsDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask, YES) lastObject]
NSString *path = [documentsDir stringByAppendingPathComponent: #"dictFile"];
myDict = [NSKeyedUnarchiver unarchiveObjectWithFile: path];