In an NSObject subclass declaration is an array:
#interface theClass : NSObject {
NSMutableArray *myArray;
}
...
#end
In the implementation's initializer:
- (id)init
{
self = [super init];
if (self) {
[myArray initWithCapacity:50];
}
return self;
}
And in a method:
- (NSMutableArray *)theMethod:(NSArray *)someArray {
...
...
[myArray addObject:anObject];
...
return myArray;
}
Yet despite the class being instantiated in my controller, any number of messages to the method leave myArray without contents.
You haven't allocated the array yet. Replace your init code with the following:
- (id)init
{
self = [super init];
if (self) {
myArray = [[NSMutableArray alloc] initWithCapacity:50];
}
return self;
}
Related
The class "PlayingCardDeck" inherits "Deck" class can not put the method
- (void) addCard:(Card *)card atTop:(BOOL)atTop
Xcode accuses me the following error:
no Known class method for selector 'addCard:atTop'
Class: PlayingCardDeck
#import "PlayingCardDeck.h"
#import "PlayingCard.h"
#implementation PlayingCardDeck
- (id)init
{
self = [super init];
if(self) {
for(NSString *suit in [PlayingCard validSuits]){
for (NSUInteger rank = 1; rank <= [PlayingCard maxRank]; rank++){
PlayingCard *card = [[PlayingCard alloc] init];
card.rank = rank;
card.suit = suit;
[PlayingCardDeck addCard:card atTop:NO];
}
}
}
return self;
}
#end
Class: Deck
#import "Deck.h"
#interface Deck()
#property (strong, nonatomic) NSMutableArray *cards;
#end
#implementation Deck
- (NSMutableArray *)cards
{
if(!_cards) _cards = [[NSMutableArray alloc] init];
return _cards;
}
- (void) addCard:(Card *)card atTop:(BOOL)atTop
{
if(atTop){
[self.cards insertObject:card atIndex:0];
} else {
[self.cards addObject:card];
}
}
- (Card *)drawRandomCard
{
Card *randomCard = nil;
if(self.cards.count){
unsigned index = arc4random() % self.cards.count;
randomCard = self.cards[index];
[self.cards removeObjectAtIndex:index];
}
return randomCard;
}
#end
thank you all for the help.
The method -addCard:atTop: is an instance method. It must be sent to an instance of a class, not the class itself. This line:
[PlayingCardDeck addCard:card atTop:NO];
is attempting to send it to the class PlayingCardDeck, not any instance of that class. That's what the error is trying to tell you.
Since that code is in the -init method of the PlayingCardDeck class, you probably meant to send the message to self:
[self addCard:card atTop:NO];
I have a IKImageBrowserView which has its own controller - BrowserController.h + .m
#interface BrowserController : NSWindowController{
NSMutableArray *_images;
}
#property (strong,nonatomic) IBOutlet IKImageBrowserView *imageBrowser;
-(void)addMultipleImages;
When I run the app for the first time, the staring image loads, but when I click a button to add other images and call a method from another class I don't get any results. I have noticed that my _imageBrowser loses the reference and becomes nil.
How could I solve this issue?
AppDelegate.m
#import "AppDelegate.h"
#import "BrowserController.h"
#implementation AppDelegate{
BrowserController *imageBrowserController;
}
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
// Insert code here to initialize your application
imageBrowserController = [BrowserController sharedManager];
}
- (IBAction)doSomething:(id)sender {
[imageBrowserController addMultipleImages];
}
#end
BrowserController.m
#import "BrowserController.h"
#interface myImageObject : NSObject
{
NSString *_path;
}
#end
#implementation myImageObject
/* our datasource object is just a filepath representation */
- (void)setPath:(NSString *)path
{
if(_path != path)
{
_path = path;
}
}
/* required methods of the IKImageBrowserItem protocol */
#pragma mark -
#pragma mark item data source protocol
/* let the image browser knows we use a path representation */
- (NSString *)imageRepresentationType
{
return IKImageBrowserPathRepresentationType;
}
/* give our representation to the image browser */
- (id)imageRepresentation
{
return _path;
}
/* use the absolute filepath as identifier */
- (NSString *)imageUID
{
return _path;
}
#end
#interface BrowserController ()
#end
#implementation BrowserController
- (id)initWithFrame:(NSRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code here.
}
return self;
}
- (void)drawRect:(NSRect)dirtyRect
{
[super drawRect:dirtyRect];
// Drawing code here.
}
- (void)awakeFromNib{
myImageObject *p;
p = [[myImageObject alloc]init];
[p setPath:[[NSBundle mainBundle]pathForResource:#"Unknown" ofType:#"jpg"]];
_images = [[NSMutableArray alloc]init];
[_images addObject:p];
[self updateDataSource];
}
- (void)updateDataSource{
[_imageBrowser reloadData];
}
-(NSUInteger) numberOfItemsInImageBrowser:(IKImageBrowserView *)aBrowser{
return [_images count];
};
-(id)imageBrowser:(IKImageBrowserView *)aBrowser itemAtIndex:(NSUInteger)index{
return [_images objectAtIndex:index];
};
- (void)updateDatasource
{
[_imageBrowser reloadData];
}
- (void)addMultipleImages{
myImageObject *p;
p = [[myImageObject alloc]init];
[p setPath:[[NSBundle mainBundle]pathForResource:#"Unknown" ofType:#"jpg"]];
_images = [[NSMutableArray alloc]init];
[_images addObject:p];
[_images addObject:p];
[_images addObject:p];
[_imageBrowser reloadData];
}
+ (id)sharedManager {
static BrowserController *sharedMyManager = nil;
#synchronized(self) {
if (sharedMyManager == nil)
sharedMyManager = [[self alloc] init];
}
return sharedMyManager;
}
#end
There is some confusion as to the name of the class where you mention it's called ImageBrowserController at the start of your question and it looks like it's called BrowserController at the end of your question.
The issue is that you allocate _images in awakeFromNib which is never called given the class is created via the singleton pattern (sharedInstance) and not loaded from a .nib file.
Therefore move the code from awakeFromNib into init and dump awakeFromNib:
BrowserController.m:
- (id)init
{
self = [super init];
if (self) {
myImageObject *p = [[myImageObject alloc]init];
[p setPath:[[NSBundle mainBundle]pathForResource:#"Unknown" ofType:#"jpg"]];
_images = [[NSMutableArray alloc]init];
[_images addObject:p];
[self updateDataSource];
}
return self;
}
Further confusion: you have implemented an initWithFrame method. Why?
I'm using an ItemController to provide a list of items to use in a tableview. I can't seem to populate the controller though, and I'm not sure why.
Here's the code for the controller class:
.h
#import <Foundation/Foundation.h>
#class Item;
#interface ItemController : NSObject
#property (nonatomic, copy) NSMutableArray *items;
- (NSUInteger)countOfList;
- (Item*)objectInListAtIndex:(NSUInteger)theIndex;
- (void)addItem:(Item *)item;
#end
.m
#import "ItemController.h"
#import "Item.h"
#interface ItemController ()
#end
#implementation ItemController
- (NSUInteger)countOfList {
return [self.items count];
}
- (Item *)objectInListAtIndex:(NSUInteger)theIndex {
return [self.items objectAtIndex:theIndex];
}
- (void)addItem:(Item *)item {
[self.items addObject:item];
}
#end
Item.m
#implementation Item
-(id)initWithName:(NSString *)name{
self = [super init];
if (self) {
_name = name;
return self;
}
return nil;
}
#end
I'm using the following code to populate the list:
ItemController* controller = [[ItemController alloc] init];
for (NSString* key in raw_data) {
NSLog(key); // This outputs the keys fine
[controller addItem:[[Item alloc] initWithName:key]];
}
NSLog([NSString stringWithFormat:#"%d",[controller countOfList]]); // Always 0
You need to initialize the array in the init methond.
- (id)init {
self = [super init];
if (self) {
self.items = [[NSMutableArray alloc] init];
}
return self;
}
You need to initialize your variable items. In your init method, call self.items = [NSMutableArray new]; and also change your array property from copy to retain.
I also believe your class ItemController should be of kind UIViewController and not NSObject.
#interface ItemController : UIViewController
You don't initialise the _items instance variable anywhere, so it's always nil. The result of any integer-returning method called on nil will be 0, so you see that the count is 0.
Im am using a pattern from the book Learning Cocos2D. I have a GameState class that is a singleton that can be saved as a state. The BOOL soundOn gets init as false the first time the class gest created, but the array levelProgress dosent. I made comments on all the lines on which I have tried to init the array.
The class uses a helper that loads and saves the data.
When i try 1 or 2 i get "instance variable 'levelProgress' accessed in class method" error.
#import <Foundation/Foundation.h>
#import "cocos2d.h"
#interface GameState : NSObject <NSCoding> {
BOOL soundOn;
NSMutableArray *levelProgress;
}
+ (GameState *) sharedInstance;
- (void)save;
#property (assign) BOOL soundOn;
#property (nonatomic, retain) NSMutableArray *levelProgress;
#end
#import "GameState.h"
#import "GCDatabase.h"
#implementation GameState
#synthesize soundOn;
#synthesize levelProgress;
static GameState *sharedInstance = nil;
+(GameState*)sharedInstance {
#synchronized([GameState class])
{
if(!sharedInstance) {
sharedInstance = [loadData(#"GameState") retain];
if (!sharedInstance) {
[[self alloc] init];
// 1. levelProgress = [[NSMutableArray alloc] init];
}
}
return sharedInstance;
}
return nil;
}
+(id)alloc
{
#synchronized ([GameState class])
{
NSAssert(sharedInstance == nil, #"Attempted to allocate a \
second instance of the GameState singleton");
sharedInstance = [super alloc];
// 2. levelProgress = [[NSMutableArray alloc] init];
return sharedInstance;
}
return nil;
}
- (void)save {
saveData(self, #"GameState");
}
- (void)encodeWithCoder:(NSCoder *)encoder {
// 3. levelProgress = [[NSMutableArray alloc] init];
[encoder encodeBool:currentChoosenCountry forKey:#"soundOn"];
[encoder encodeObject:levelProgress forKey:#"levelProgress"];
}
- (id)initWithCoder:(NSCoder *)decoder {
if ((self = [super init])) {
// 4. levelProgress = [[NSMutableArray alloc] init];
soundOn = [decoder decodeBoolForKey:#"soundOn"];
levelProgress = [decoder decodeObjectForKey:#"levelProgress"];
}
return self;
}
#end
Solution:
*I just added av init method...*
-(id)init {
self = [super init];
if (self != nil) {
levelProgress = [[NSMutableArray alloc] init];
}
return self;
}
Try this (this code may contain syntax or logic errors - I wrote it in notepad):
#interface GameState : NSObject <NSCoding>
#property (nonatomic, readwrite) BOOL soundOn;
#property (nonatomic, retain) NSMutableArray *levelProgress;
+ (GameState *)sharedState;
- (void)writeDataToCache;
#end
//
#implementation GameState
#synthesize soundOn, levelProgress;
#pragma mark - Singleton
static GameState *sharedState = nil;
+ (void)initialize {
static BOOL initialized = NO;
if (!initialized) {
initialized = YES;
if ([[NSFileManager defaultManager] fileExistsAtPath:[NSString stringWithFormat:#"%#/gameState", pathCache]]) {
NSData *encodedObject = [[NSData alloc] initWithContentsOfFile:[NSString stringWithFormat:#"%#/gameState", pathCache]];
data = [NSKeyedUnarchiver unarchiveObjectWithData:encodedObject];
}
else
data = [[GameState alloc] init];
}
}
+ (GameState *)sharedState {
return sharedState;
}
#pragma mark - Initialization
- (id)init {
if (self = [super init]) { // will be inited while application first run
soundOn = NO;
levelProgress = [[NSMutableArray alloc] init];
return self;
}
return nil;
}
#pragma mark - Coding Implementation
- (void)writeDataToCache { // use this method to save current state to cache
NSData *encodedObject = [NSKeyedArchiver archivedDataWithRootObject:self];
if([[NSFileManager defaultManager] fileExistsAtPath:[NSString stringWithFormat:#"%#/GameState", pathCache]])
[[NSFileManager defaultManager] removeItemAtPath:[NSString stringWithFormat:#"%#/GameState", pathCache] error:nil];
[[NSFileManager defaultManager] createFileAtPath:[NSString stringWithFormat:#"%#/GameState", pathCache] contents:encodedObject attributes:nil];
NSLog(#"GameState was saved successfully.");
}
- (void)encodeWithCoder:(NSCoder*)encoder {
[encoder encodeBool:self.soundOn forKey:#"soundOn"];
[encoder encodeObject:self.levelProgress forKey:#"levelProgress"];
}
- (id)initWithCoder:(NSCoder*)decoder {
if ((self = [super init])) {
self.soundOn = [decoder decodeBoolForKey:#"soundOn"];
self.levelProgress = [decoder decodeObjectForKey:#"levelProgress"];
NSLog(#"GameState was inited successfully");
return self;
}
return nil;
}
#end
1 & 2 are the same (and should not work, since levelProgress is an instance variable), 3 and 4 should be encoding/decoding the array, not initializing it anew.
1 and 2 are a mistake - you can't access instance variable without specifying an instance.
You can fix 1 by changing the line to sharedInstance.levelProgress = ....
2 is just a bad idea, you're breaking common convention of initializing using init... methods, it may surprise and cause problems for an other programmer who'll be working on the same code later.
3 and 4 are ok but if loadData fails they will not be executed and the object will be initialized with ordinary init and the array will be nil pointer:
[[self alloc] init];
you should also override init and initialize the properties there.
If I create a custom initWith for an object do I essentially include the code I would add should I want to override init?
-(id) init {
self = [super init];
if (self) {
NSLog(#"_init: %#", self);
}
return(self);
}
e.g.
-(id) initWithX:(int) inPosX andY:(int) inPosY {
self = [super init];
if(self) {
NSLog(#"_init: %#", self);
posX = inPosX;
posY = inPosY;
}
return(self);
}
gary
You can create one designated initializer that accepts all parameters that you want to make available in initialization.
Then you call from your other -(id)init your designated initializer with proper parameters.
Only the designated initializer will initialize super class [super init].
Example:
- (id)init
{
return [self initWithX:defaultX andY:defaultY];
}
- (id)initWithPosition:(NSPoint)position
{
return [self initWithX:position.x andY:position.y];
}
- (id)initWithX:(int)inPosX andY:(int)inPosY
{
self = [super init];
if(self) {
NSLog(#"_init: %#", self);
posX = inPosX;
posY = inPosY;
}
return self;
}
The designated initializer is -(id)initWithX:andY: and you call it from other initializers.
In case you want to extend this class you call your designated initializer from subclass.
I'd suggest creating one main initializer that handles most of the work. You can then create any number of other initializers that all call this main one. The advantage of this is if you want to change the initialization process, you'll only have to change one spot. It might look like this:
-(id) initWithX:(float)x {
if (self = [super init]) {
/* do most of initialization */
self.xVal = x;
}
return self;
}
-(id) init {
return [self initWithX:0.0f];
}
In this example initWithX: is our main initializer. The other initializer (init) simply calls initWithX: with a default value (in this case 0).
Yes, that's exactly how I do it. One slight change will cut out a line of code:
if (self = [super init]) {
As opposed to:
self = [super init];
if(self) {
For modern Objective-C ...
UDFile.h
#import <Foundation/Foundation.h>
#interface UDFile : NSObject
#property (nonatomic, strong) NSString *name;
- (instancetype)initWithName:(NSString *)name NS_DESIGNATED_INITIALIZER;
#end
UDFile.m
#import "UDFile.h"
#implementation UDFile
- (instancetype)initWithName:(NSString *)name {
self = [super init];
if (self) {
_name = [name copy];
}
return self;
}
- (instancetype)init {
return [self initWithPathname:#""];
}
Sometimes, you want to reuse some initialisation code and modify the behaviour only slightly for specific initialisers. In this case, I do the following:
- (id) init
{
self = [super init];
if (!self) return nil;
// These values are always initialised this way
ivar1 = 10;
ivar2 = #"HellO";
ivar3 = [[NSMutableArray alloc] initWithCapacity:10];
ivar4 = 22;
return self;
}
- (id) initWithIvar4:(int) aValue
{
// call -init on self, which will call -init on super for us, and set
// up ivar1, ivar2, ivar3, and ivar4.
self = [self init];
if (!self) return nil;
// Change ivar4 from the default 22 to whatever aValue is.
ivar4 = aValue;
return self;
}