Monsters/Enemies on Platforms(like on Doodlejump)Cocos2d - iphone

Question

I'm new here so i hope you can help me.
I am following a tutorial on making simple cocos2d game
Ray Wenderlich's Tutorial
I implemented it on another game a jumping one like doodle jump.
in the said tutorial the monsters/targets are moving freely coming from the right to the left side of the screen. when i implement it on my app the monsters are like flying from left to right. What if i want the monsters to stand on the platforms just like the one on doodle jump? what particular things will i do?
PS:i tried some other things on google but none works
Here is the code of the monsters/targets:
- (void)initPlatforms {
// NSLog(#"initPlatforms");
currentPlatformTag = kPlatformsStartTag;
while(currentPlatformTag < kPlatformsStartTag + kNumPlatforms) {
[self initPlatform];
currentPlatformTag++;
}
[self resetPlatforms];
}
- (void)initPlatform {
CGRect rect;
switch(random()%2) {
case 0: rect = CGRectMake(608,64,102,36); break;
case 1: rect = CGRectMake(608,128,90,32); break;
}
AtlasSpriteManager *spriteManager = (AtlasSpriteManager*)[self getChildByTag:kSpriteManager];
AtlasSprite *platform = [AtlasSprite spriteWithRect:rect spriteManager:spriteManager];
[spriteManager addChild:platform z:3 tag:currentPlatformTag];
}
-(void)addTarget {
Sprite *target = [Sprite spriteWithFile:#"komodo.png"];
target.position = ccp(300,200);
[self addChild:target];
CGSize winSize = [[Director sharedDirector]winSize];
int minX = target.contentSize.height/2;
int maxX = winSize.height -target.contentSize.height/2;
int rangeX = maxX - minX;
int actualX = (arc4random() % rangeX) +minX;
int minDuration = 2.0;
int maxDuration = 4.0;
int rangeDuration = maxDuration - minDuration;
int actualDuration = (arc4random() % rangeDuration) + minDuration;
id actionMove = [MoveTo actionWithDuration:actualDuration position:ccp(-target.contentSize.width,actualX)];
id actionMoveDone = [CallFuncN actionWithTarget:self selector:#selector(spriteMoveFinished:)];
[target runAction:[Sequence actions:actionMove, actionMoveDone,nil]];
target.tag = 1;
[_targets addObject:target];
}
Thanks to those who will help... you are so nice.

Answer 1

This is a pretty broad question unfortunately, which makes it difficult to answer in any definitive terms. If you are hoping to create actual platforms that can be bounced on (in a doodle jump manner) you are going to need to implement collision detection between the Monsters and the Platform ccNodes. There are numerous tutorials online for cocos2d collision detection, both simple implementation and the more advanced box 2d/chipmunk based solutions.
If you are looking to clone doodle jump fairly closely, there is an open source version of a clone available on github here - though I've not actually looked at the code.
Finally, if you mean that you simply want to restrict the movement of the monsters to a particular area of the screen (so they don't keep running off the edge) you just need to position the target to an area on the screen and alter theccAction so that the ccMoveTo uses the left most point of the 'platform' as the furthest point left it can move to and the right most point as the furthest right. (I'll confess I've not played Doodle Jump so have no idea what the enemies actually do).
If the enemies run back and forth across the platform you should look into using ccRepeatForever on your movement sequence and have two destination positions in the CCSequence : one that moves the monster to the left of the platform, the other to move it to the right.
Additional Info
Ok, I see what you are trying to do. This should get you started:
Platforms are created in initPlatforms. This calls initPlatform a number of times. This grabs an image from the AtlasSprite for the platform, creates a ccSprite for each platform and assigns it a unique tag.
Then, in - (void)step:(ccTime)dt it loops through all the platforms and moves them to their correct location based on how far the bird has moved:
for(t; t < kPlatformsStartTag + kNumPlatforms; t++) {
AtlasSprite *platform = (AtlasSprite*)[spriteManager getChildByTag:t];
//etc...
So, the bit you are waiting for:
If you want to add a monster to these platforms, you will have to follow a similar pattern. To get started try something like this (You will want to have a cleaner design than this though but it should put you on the right track)
in initPlatform add the following to the end of the function
// add a monster sprite
AtlasSprite *monster = [AtlasSprite spriteWithRect:CGRectMake(608,128,64,64) spriteManager:spriteManager];
[spriteManager addChild:monster z:3 tag:currentPlatformTag + 1000];
(I've just grabbed an image from the existing Atlas. You could replace the above with your actual 'Monster' sprite object. Notice I add 1000 to thecurrentPlatformTag. This is just for testing; you should have a monsterTag implementation eventually.
So now every platform has a 'monster' (Again, you will only want to target random platforms)
so we need to update the positions for the monsters.
In - (void)step:(ccTime)dt directly after you get the current platform
AtlasSprite *platform = (AtlasSprite*)[spriteManager getChildByTag:t];
You now also need to get the current monster (remembering to use the updated tag value we created for 'monsters':
AtlasSprite *monster = (AtlasSprite*)[spriteManager getChildByTag:t + 1000];
Then, a few lines below where we reposition the platform we will need to reposition the monster
platform.position = pos;
// We update the monster and set it a 32 pixels above the platform:
monster.position = ccp(pos.x, pos.y + 32);
So now each platform has a monster on it whose y position moves with the the platforms :-)
Hope this helps