Constantly moving object with Cocos2d - cocos2d-iphone

Question

I'm looking for some guidance on how, using Cocos2d, I can have an object (let's say a rocket) that is in constant motion at a constant speed, and I have two buttons to simply change its direction.
I've found a few pieces of information on how to change the orientation of the rocket, however I'm stuck on just having the rocket be in constant motion.
I'll later want to make the rocket be able to fly off the screen and re-appear on the other side of the screen, but that's for another question (I've found some help on this already).
I'm new to Cocos2d and have searched for a few hours, but haven't been able to find what I'm after.
Could somebody point me in the right direction in being able to get my rocket constantly moving, and responding to changes in direction?

Answer 1

So, here's a first pass at how you could do something like that:
// ProjectileTest holds a projectile class that simply knows how to
move itself
// WrapBoundaryTest is the example scene showing potential usage of
ProjectileTest
ProjectileTest.h
#import "cocos2d.h"
#interface ProjectileTest : CCNode
{
CCSprite *sprite;
CGPoint velocity;
CGRect bounds;
BOOL isActive;
float steerAmount;
}
#property CCSprite *sprite;
#property CGPoint velocity;
#property CGRect bounds;
#property BOOL isActive;
#property float steerAmount;
+(id) projectileWithBounds:(CGRect) boundary
andVelocity:(CGPoint) v
andSteeringAmount:(float) steeringAmount;
-(void) step:(CCTime) dt;
-(void) steerLeft;
-(void) steerRight;
#end
ProjectileTest.m
#import "ProjectileTest.h"
#implementation ProjectileTest
#synthesize sprite, velocity, bounds, isActive, steerAmount;
+(id) projectileWithBounds:(CGRect) boundary andVelocity:(CGPoint) v andSteeringAmount:(float) steeringAmount
{
ProjectileTest *proj = [[self alloc] init];
proj.bounds = boundary;
proj.velocity = v;
proj.steerAmount = steeringAmount;
proj.isActive = YES;
[proj calculateAngleForVelocity: v];
return proj;
}
-(id) init
{
if(( self = [super init]))
{
sprite = [CCSprite spriteWithImageNamed:#"Icon.png"];
[self addChild:sprite];
[sprite setScale:0.50f];
bounds = CGRectZero;
velocity = CGPointZero;
isActive = NO;
steerAmount = 1.0f;
}
return self;
}
-(void) calculateAngleForVelocity:(CGPoint) v
{
float rads = ccpToAngle(v);
float degs = -CC_RADIANS_TO_DEGREES(rads);
sprite.rotation = degs + 90.0f;
}
-(void) steerLeft
{
[self steer: YES];
}
-(void) steerRight
{
[self steer: NO];
}
-(void) steer:(BOOL) left
{
if(left)
{
velocity = ccpRotateByAngle(velocity, CGPointZero, -CC_DEGREES_TO_RADIANS(-steerAmount));
}
else // right
{
velocity = ccpRotateByAngle(velocity, CGPointZero, -CC_DEGREES_TO_RADIANS(steerAmount));
}
}
-(void) step:(CCTime)dt
{
if(isActive)
{
if(CGRectContainsPoint(bounds, self.position))
{
self.position = ccpAdd(self.position, velocity);
[self calculateAngleForVelocity: velocity];
}
else
{
float nudge = 0.5f;
if(self.position.x >= bounds.size.width && velocity.x > 0.0f)
{
self.position = ccp(bounds.origin.x + nudge, self.position.y);
}
else if(self.position.x <= bounds.origin.x && velocity.x < 0.0f)
{
self.position = ccp(bounds.size.width - nudge, self.position.y);
}
if(self.position.y >= bounds.size.height && velocity.y > 0.0f)
{
self.position = ccp(self.position.x, bounds.origin.y + nudge);
}
else if(self.position.y <= bounds.origin.y && velocity.y < 0.0f)
{
self.position = ccp(self.position.x, bounds.size.height - nudge);
}
}
}
}
#end
WrapBoundaryTest.h
#import "cocos2d.h"
#import "cocos2d-ui.h"
#interface WrapBoundaryTest : CCScene
{
NSMutableArray *projectiles;
CCButton *left;
CCButton *right;
}
#property __strong NSMutableArray *projectiles;
+(id) scene;
#end
WrapBoundaryTest.m
#import "WrapBoundaryTest.h"
#import "ProjectileTest.h"
#implementation WrapBoundaryTest
#synthesize projectiles;
+(id) scene
{
return [[self alloc] init];
}
-(id) init
{
if(( self = [super init]))
{
projectiles = [NSMutableArray array];
CGRect projectileBounds = CGRectMake(
0.0f,
0.0f,
[CCDirector sharedDirector].designSize.width,
[CCDirector sharedDirector].designSize.height
);
CGPoint origin = ccp(200.0f, 150.0f);
[self addProjectileWithBoundsRect:projectileBounds andVelocity:ccp( 1.0f, 5.0f) andSteeringAmount:2.0f atStartingPosition:origin];
[self addProjectileWithBoundsRect:projectileBounds andVelocity:ccp(-1.0f, -5.0f) andSteeringAmount:1.0f atStartingPosition:origin];
[self addProjectileWithBoundsRect:projectileBounds andVelocity:ccp(-1.0f, 1.0f) andSteeringAmount:0.5f atStartingPosition:origin];
[self addProjectileWithBoundsRect:projectileBounds andVelocity:ccp( 8.0f, 1.0f) andSteeringAmount:7.5f atStartingPosition:origin];
left = [CCButton buttonWithTitle:#"Left" fontName:#"Arial" fontSize:16.0f];
left.positionType = CCPositionTypeNormalized;
left.position = ccp(0.1f, 0.1f);
[self addChild:left];
right = [CCButton buttonWithTitle:#"Right" fontName:#"Arial" fontSize:16.0f];
right.positionType = CCPositionTypeNormalized;
right.position = ccp(0.9f, 0.1f);
[self addChild:right];
}
return self;
}
-(void) addProjectileWithBoundsRect:(CGRect) boundsRect
andVelocity:(CGPoint) velocity
andSteeringAmount:(float) steeringAmount
atStartingPosition:(CGPoint) startingPosition
{
ProjectileTest *proj = [ProjectileTest projectileWithBounds: boundsRect
andVelocity: velocity
andSteeringAmount: steeringAmount
];
proj.position = startingPosition;
[self addChild:proj];
[projectiles addObject:proj];
}
-(void) update:(CCTime)delta
{
for(ProjectileTest *p in projectiles)
{
if(left.touchInside)
{
[p steerLeft];
}
if(right.touchInside)
{
[p steerRight];
}
[p step:delta];
}
}
#end
// HTH