I'm having trouble with Objective C.
I'm trying to call a block after I've moved a sprite
The short version of what i'm trying to achieve is that i want to move all of the enemies in an array, and when each one finishes moving i want to check whether it has collided.
The simplified code below shows what i'm trying to do.
My Actor class is defined like this
// -----------------------------
// Actor.h
#import <Foundation/Foundation.h>
#import "cocos2d.h"
#import "ScreenObject.h"
typedef void (^actorMoveComplete)(void);
#interface Actor : ScreenObject
{
// actorMoveComplete onMoveComplete;
}
#property (nonatomic) BOOL isMoving;
#property (readwrite, copy) actorMoveComplete onMoveComplete;
#property (nonatomic, retain) CCSprite* sprite;
-(void) moveTo:(CGPoint)targetPosition Speed:(float) speed withCallback:(actorMoveComplete)moveComplete;
#end
// -----------------------------
// Actor.m
#import "Actor.h"
#implementation Actor
#synthesize onMoveComplete;
#synthesize sprite;
-(void) moveTo:(CGPoint)targetPosition Speed:(float) speed withCallback:(actorMoveComplete)moveComplete;
{
onMoveComplete = moveComplete;
id actionMove = [CCMoveTo actionWithDuration:speed position:targetPosition];
id actionMoveDone = [CCCallFuncN actionWithTarget:self selector:#selector(spriteMoveFinished:)];
[super.sprite runAction:[CCSequence actions:actionMove, actionMoveDone, nil]];
}
-(void) spriteMoveFinished:(id) sender
{
isMoving = NO;
if (onMoveComplete != nil)
onMoveComplete();
}
#end
As you can see i'm trying to store the block in an onMoveComplete parameter (i've also tried it in a private variable), and then call it once the sprite move has completed.
In my calling class i'm iterating through a bunch of actors (enemies) and i want to call this anonymous code block for each actor once the move has completed:
{
[self checkForCollision:enemy];
}
My calling class looks like this.
//------------------------------
//
// GameLayer.h
#import "cocos2d.h"
#import "Actor.h"
#interface GameLayer : CCLayerColor
{
}
#property (nonatomic, copy) NSMutableArray *enemies;
- (void) updateEnemies;
- (void) checkForCollision:(Actor*)actor;
- (BOOL) isMapGridClear:(CGPoint)mapGrid excludeActor:(Actor*)actor;
#end
//------------------------------
// GameLayer.m
#import "GameLayer.h"
#implementation GameLayer
#synthesize enemies;
- (void) updateEnemies
{
for (Actor *enemy in enemies)
{
//
CGPoint newPosition = [self getNewPosition:enemy]; /* method to figure out new position */
[enemy moveDelta:ccp(dX, dY) Speed:enemySpeed withCallback:^{
[self checkForCollision:enemy];
}];
}
}
- (void) checkForCollision:(Actor*)actor
{
if (![self isMapGridClear:actor.gridPosition excludeActor:actor])
{
actor.isCrashed=YES;
[actor loadSprite:self spriteImage:#"crashed.png"];
}
}
- (BOOL) isMapGridClear:(CGPoint)mapGrid excludeActor:(Actor*)actor
{
/* Actual method figures out if there was a collision */
return YES;
}
#end
Unfortunately when I call the onMoveComplete block, i keep getting an EXC_BAD_ACCESS error
Interestingly, if I try to call the block inside the moveTo method, it works (but of course i want this to trigger AFTER the movement has completed).
Can anyone help me with what i'm doing wrong. Am I even using the correct mechanism?
(Apologies for the poorly formatted, incomplete code segments)
You correctly declared your property as copy, but you are setting your instance variable directly to the address of the block without using the generated accessors. That means the block won't get copied and gets destroyed before it is called.
Assign your block using self.onMoveCompleted = moveCompleted and you will be fine.
Related
In my AppDelegate.m, I am doing something like this
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
#try {
// initalizing Meeting config
MeetingConfig *config = [[MeetingConfig alloc] init];
NSLog(#"Initalized Meeting Config: %#", config);
[config setRoomName:#"test123"];
NSLog(#"SetRoom name for Meeting config: %#", config.roomName);
NSString *clientId = #"";
NSLog(#"Unused Client id is: %#", clientId);
//Call UIView from here
}#catch (NSException *exception) {
NSLog(#"exception: %#", exception);
}
return YES;
}
Where my MeetingConfig.m file looks like this
#implementation MeetingConfig
- (id) init
{
if (self = [super init]) {
self.apiBase = #"https://api.in";
self.showSetupScreen = false;
self.autoTune = true;
}
return self;
}
- (void) setAuthToken:(NSString *)authToken
{
self.authToken = authToken;
}
- (void) setApiBase:(NSString *)apiBase
{
self.apiBase = apiBase;
}
// more code
and MeetingConfig looks like this
#import <Foundation/Foundation.h>
#interface MeetingConfig : NSObject
#property (nonatomic, assign) NSString* roomName;
#property (nonatomic, assign) NSString* authToken;
#property (nonatomic, assign)Boolean autoTune;
#property (nonatomic, assign)NSString* apiBase;
#property (nonatomic, assign)Boolean showSetupScreen;
- (void) setRoomName:(NSString *)roomName;
- (void) setAuthToken:(NSString *)authToken;
- (void) setShowSetupScreen:(Boolean)showSetupScreen;
- (void) setAutoTuneEnabled:(Boolean)autoTune;
- (id) init;
#end
Can someone help me in determining what I could be doing wrong here? and why doesn't it log exception in NSLog? Also, I am super new to objective C (i have been asked to stick with Objective c) and if anyone have any suggestion in regards to the code then please let me know.
Error
You're using assign for reference/pointer types: #property retain, assign, copy, nonatomic in Objective-C
They should probably be declared copy, because this is a kind of value object, I think.
No exceptions were caught because no exceptions were thrown. Throwing/catching exceptions for control flow is not common in Objective-C
You don't need to write explicit setter functions for #properties
You should prefer to use BOOL type instead of Boolean, with values of YES/NO instead of true/false.
You should return instancetype not id from init, at least in reasonably modern Objective C
Consider making an initialiser that takes all the properties (initWithRoomName:clientID:) and make them read only once set
You don't need to declare -(id) init in your header since it gets that from NSObject
I am learning Objective-C inheritance and my program is getting lost in a recursive loop and won't come out. It gets hung up when calling a getter function.
I am using XCode version: Version 6.2 (6C101)
My program is given below
Vehicle.h
#ifndef exercise_2_Vehicle_h
#define exercise_2_Vehicle_h
#import <Foundation/Foundation.h>
#interface Vehicle : NSObject
#property float speed;
-(void) start;
-(void) stop;
-(void) park;
#end
#endif
Vehicle.m
#import "Vehicle.h"
#implementation Vehicle
-(void) setSpeed:(float)speed {
self.speed = speed;
}
-(float) speed {
return self.speed;
}
-(void) start {
NSLog(#"Starting the vehicle");
}
-(void) stop {
NSLog(#"Stopping the vehicle");
}
-(void) park {
NSLog(#"Parking the vehicle");
}
#end
Car.h
#ifndef exercise_2_Car_h
#define exercise_2_Car_h
#import "Vehicle.h"
#interface Car : Vehicle
#property (nonatomic) NSString* make;
-(Car*) initMake: (NSString*) make;
-(NSString*) make;
#end
#endif
Car.m
#import "Car.h"
#implementation Car
-(Car*) initMake:(NSString *)make {
self = [super init];
if (self) {
self.make = make;
}
return self;
}
-(NSString*) make {
return self.make;
}
#end
main.m
#import <Foundation/Foundation.h>
#import "Car.h"
#import "Vehicle.h"
int main(int argc, const char * argv[]) {
#autoreleasepool {
// insert code here...
Car* car = [[[Car alloc] init] initMake: #"Camry"];
//[car setSpeed:45];
NSLog(#"The model initialized is ");
[car make];
// [car speed];
}
return 0;
}
The issue you have is caused by creating the property for speed:
#property float speed;
and overriding setSpeed: method.
When you create #property compiler adds two methods for you, in your example setSpeed and speed.
This command:
self.speed = speed;
is equal to:
[self setSpeed: speed];
and inside setSpeed you have this command again which cause the loop. In your example you can remove both methods (setSpeed and speed) because compiler will add it for you. If you need it because you want to do some customisation you should use _speed instead self.speed.
_speed is backed variable added by compiler when using #property.
Change your method to:
-(void) setSpeed:(float)speed {
_speed = speed;
}
to remove the infinite loop.
In the
- (NSString*)make;
use
return _make
instead. The same with the speed.
If you return "self.x" in a getter method, then it's going to try and call the method again because you're requesting it on self. XCode will automatically convert the properties into variables that can be accessed with an '_' character, so you don't need to do any extra work.
You could also ignore our advice and remove both the "speed" and "make" getter methods you have made, because XCode automagically creates them for you.
Is it possible to extend an derived class from NSManagedObject? I'm asking this because I tried to do it. My entity looks like this:
So this means a class similar to the following code should be generated:
#import <Foundation/Foundation.h>
#interface Player : NSManagedObject
#property (nonatomic, copy) NSNumber* orderNumber;
#property (nonatomic, copy) NSString *name;
#end
.m file
#import "Player.h"
#implementation Player
#dynamic name, orderNumber;
#end
This two variables are saved to the SQLite database.
Now since I need some additional variables for the player I just added them to the class. It still worked.
#import "Player.h"
#implementation Player
#dynamic name, orderNumber;
- (id) init
{
self = [super init];
if (self != nil)
{
[self reset];
}
return self;
}
#synthesize isStillInGame = _isStillInGame;
- (void) reset
{
_isStillInGame = TRUE;
}
- (void) setOutOfGame
{
_isStillInGame = FALSE;
}
#end
But now when I change the isStillInGame bool, all instances of the Player Class are changed. Is this normal or do I have an error in my code?
A second question I can't answer is, why I can't access the object variables while debugging. When I try to watch an Player instance variable I just see this:
Is it possible to see more?
I'm using Cocos2d and I can not access properties of an object from another one.
Here I just want to get the hitpoints of a ship form a scene. It fails and returns an error : uncaught exception 'NSInvalidArgumentException', reason: '-[CCSprite hitpoints]: unrecognized selector...
As hitpoints is declared in the interface of the class Ship I can't figure out why.
The only thing I understand is that it's a inhéritance issue.
Let's show some code :
Ship.h
#import <Foundation/Foundation.h>
#import "cocos2d.h"
#interface Ship : CCSprite {
int hitpoints;
}
#property (nonatomic, assign) int hitpoints;
- (id)init;
#end
Then Ship.m
#import "Ship.h"
#implementation Ship
#synthesize hitpoints;
- (id)init
{
hitpoints = 3;
self = [CCSprite spriteWithImageNamed:#"ship.png"];
return self;
}
#end
In the Scene.m
#import "Ship.h"
#implementation Scene
{
Ship *_player;
}
- (id)init
{
_player = [[Ship alloc] init];
[self addChild:_player];
// ERROR HERE
NSLog(#"%s = %d", "_player hp", [_player hitpoints]);
}
Thank you.
I suspect the issue is with your init method; you shouldn't be accessing properties until the object is initialised and you should be calling [super initWith...] instead of the class creation method.
I would suggest the following changes:
Ship.h:
#interface Ship : CCSprite
#property (nonatomic, assign) int hitpoints;
#end
Ship.m:
#import "Ship.h"
#implementation Ship
#synthesize hitpoints;
- (id)init
{
self = [super initWithImageNamed:#"ship.png"];
if (self) {
self.hitpoints = 3;
}
return self;
}
#end
Always use object.property when referencing a property, even when object == self.
This:
- (id)init
Means "a method that returns any kind of object, which is called init".
This:
self = [CCSprite spriteWithImageNamed:#"ship.png"];
Means "create an instance of CCSprite". You then return that instance.
So _player ends up being an instance of CCSprite. CCSprite does not implement hitpoints so the exception is raised.
What are you actually trying to achieve? A subclass of CCSprite? trojanfoe has covered how to write a proper init for that. Things I think you need to know:
all classes look the same at runtime;
declaring the type of class pointers helps humans and the compiler to check your code but doesn't change the code generated;
some Objective-C patterns (probably most notably including class clusters) are built around init being able to return any kind of class — it's a useful feature, not a misfeature.
I'm trying to teach myself Objective-C and as an exercise, I'm trying to write an app with one button and one label. When I click on the button, I want to trigger a calculation then see the results in the label. The following code compiles and runs with no errors or warnings but as far as I can tell, the [object method] 'call' doesn't do anything. I've spent hours on this and just don't see what's wrong. Can anyone explain the problem? Thanks.
*** testMethodViewController.h ****
#import <UIKit/UIKit.h>
#import "testBrain.h"
#interface testMethodViewController : UIViewController
{
IBOutlet UILabel *display;
testBrain *model;
}
- (IBAction)cellPressed:(UIButton *)sender;
#end
*** testMethodViewController.m ****
#import "testMethodViewController.h"
#implementation testMethodViewController
- (testBrain *)model
{
if (!model) {model = [[testBrain alloc] init];}
return model;
}
- (IBAction)cellPressed:(UIButton *)sender
{
int x = [model check:3]; //This method call doesn't work. But gets no errors.
NSLog(#"Results from model: %i", x); //Says x = 0, but I expect 6
NSString *xAsString = [NSString stringWithFormat: #"testBrain: %i", x];
display.text = xAsString; //Label is updated and displays: testBrain: 0
} //I expect: testBrain: 6
#end
*** testBrain.h ****
#import <Foundation/Foundation.h>
#interface testBrain : NSObject {}
- (int) check:(int) anInteger;
#end
*** testBrain.m ****
#import "testBrain.h"
#implementation testBrain
- (int) check:(int) anInteger //3 passed as the parameter.
{
int r = anInteger + anInteger;
NSLog(#"inside check %i", r); //Debugging line: doesn't print.
return r;
}
#end
When this code runs:
int x = [model check:3];
model is nil. In Objective-C, messages sent to nil silently do nothing, and return 0. So, as you see, x is 0 and -check: is never called.
Apparently you were expecting this method to be called automatically:
- (testBrain *)model
{
if (!model) {model = [[testBrain alloc] init];}
return model;
}
However, that method will be called only if you do it yourself, by saying [self model] or self.model. So, this line would fix it:
int x = [[self model] check:3];
Try it and see.
Going a little further: It would be clearer to remove the model method entirely, and create the instance variable model when the UIViewController is created. That way, we can guarantee that model is valid anytime any code in the testMethodViewController class runs.
You would do that by overriding UIViewController's designated initializer:
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Now you can initialize your instance variables
model = [[testBrain alloc] init];
}
return self;
}
With your model method, you are halfway towards Lazy Instantiation, however to properly achieve this, you must always acess the lazily instantiated object through its accessor method. You aren't doing this in your button action, so your messages are going to nil, which is silently ignored.
This is one of the reasons you often see instance variables in objective-c declared with a leading or trailing underscore. If you then typed model anywhere in the rest of your class, it would be a compiler error, forcing you to use the accessor. Typically this is implemented with properties and the synthesize statement:
In your interface:
#property (nonatomic, strong) TestBrain* model;
In your implementation:
#synthesize model = model_;
Your model method would be:
-(TestBrain*)model
{
if (!model_)
model_ = [[TestBrain alloc] init];
return model_;
}
You would then use self.model instead of model throughout the rest of the class.
If you are just starting out, the Stanford iOS course on iTunes U is an excellent resource, a lot of this sort of material is covered.
int x = [model check:3];
This line should be:
int x = [self.model check:3];
you are almost there. You need to use #property and #synthesize in order to complete this. The #synthesize directive will direct the compiler to create the setters and getters for a particular property. The #synthesize directive tells the compiler that variable is a property. Properties allow you to use the dot syntax. i.e. self.model which will automatically the call the getter or setter method, depending on the context.
In your testMethodViewController.h file change it to look like this:
#interface testMethodViewController : UIViewController
{
IBOutlet UILabel *display;
testBrain *model;
}
#property (nonatomic,retain) testBrain *model;
- (IBAction)cellPressed:(UIButton *)sender;
#end
then in the .m implementation you need to use #synthesize after the #implementation. Like this:
#implementation testMethodViewController
#synthesize model; // tells the compiler to synthesize the setter and getter for you
- (testBrain *)model
{
if (!model) {model = [[testBrain alloc] init];}
return model;
}
then in your cellPressed: method, you need to use self.model in order for the getter to be called:
- (IBAction)cellPressed:(UIButton *)sender
{
int x = [self.model check:3]; //This method call doesn't work. But gets no errors.
NSLog(#"Results from model: %i", x); //Says x = 0, but I expect 6
NSString *xAsString = [NSString stringWithFormat: #"testBrain: %i", x];
display.text = xAsString; //Label is updated and displays: testBrain: 0
}
Hope this helps.
I dont see anywhere in the testMethodViewController.h file
IBOutlet UIButton *button;
Also check if u have properly connected all IBOutlet, IBAction & delegate, datasource.