iOS - custom initialization method for view controllers when using storyboard - ios

Question

I've read several posts similar to this one but I found them too specific. What I really want is a more general answer. According to Apple's view controller programming guide, viewDidLoad: should be used to "Allocating or loading data to be displayed in your view". If I have some data that has nothing to do with display, where should I initialize them?
Some posts suggests that initialization could be done in initWithCoder: when the view controller is initialized via a storyboard. I've tried to initialize an array in initWithCoder:, but after that it turned out that the array is still empty. So can we write a designated initializer to initialize this kind of data?
Here is the code:
- (id)initWithCoder:(NSCoder *)aDecoder
{
if (self = [super initWithCoder:aDecoder]) {
// load notes
NSString * path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
_notes = [[PWCNotes alloc] initNotesWithFilename:self.docTitle path:path numberOfPages:self.numberOfPages];
_index = 0;
}
return self;
}
Here is the designated initializer method for PWCNotes
- (id)initNotesWithFilename:(NSString *)fileName path:(NSString *)path numberOfPages:(int)numberOfPages
{
if (!(self = [super init])) {
return nil;
}
_filePath = [path stringByAppendingString:[NSString stringWithFormat:#"/%#/notes.txt", fileName]];
BOOL exists = [[NSFileManager defaultManager] fileExistsAtPath:self.filePath];
if (!exists)
{
// if file does not exist, create one and initialize the content
_notes = [[NSMutableArray alloc] init];
[[NSFileManager defaultManager] createFileAtPath:self.filePath contents:nil attributes:nil];
NSString * emptyString = #"Add Notes Here!";
for (int i = 0; i < numberOfPages; ++i)
{
[self.notes addObject:emptyString];
}
// write content of the array to the file
[self.notes writeToFile:self.filePath atomically:YES];
}
else
{
// otherwise, load it from the text file
_notes = [[NSMutableArray alloc] initWithContentsOfFile:self.filePath];
}
return self;
}
PWCNotes class has as a property a mutable array of NSString *s. When I call [self.notes.notes getObjectAtIndex:self.index], an NSRangeException is thrown, saying that I'm trying to access the object at index 0 in an empty array. Am I missing something?

Answer 1

viewDidLoad is the best place if you need to use the data only once the view appears, which is usually the case for View Controllers, as they only exists for managing views.
It's the best place because it is the one that's called in any case, no matter how the class got initialized.
If you really wanted to have the data ready earlier, you could implement an +initialize or +load method (NSObject +load and +initialize - What do they do?) instead, but that's not really what you should do in a View Controller.