Control individual members of a group

[JFish]

Hello all.  I just discovered Phaser.io and think it is great.  I am a bit stuck, however, on how to manipulate members of a group.  I have a space shooter where I spun up about a dozen enemies within a group.  Now I want to select individual members of the groups to move toward the player in some pattern.  I can't figure out how to get just one member of the group.  I tried something like:

var leader=enemies.getFirstAlive();leader.x-=1;

 but it did not work.  Also, what if I wanted it to be a random enemy that was alive?  Any guidance would be most appreciated.

 

 

[j0hnskot]

I don't know if i clearly understand what you ask, sorry for this.  This may be helpful for you  http://gamemechanicexplorer.com/#follow-3

Also, about the random enemy check Group.getRandom()

[JUL]

Use body.velocity.x instead of .x

 

http://examples.phaser.io/_site/view_full.html?d=games&f=invaders.js&t=invaders

[JFish]

Thanks @j0hnkot and @Jul

 

@j0hnkot  Group.getRandom() does indeed look useful, thanks.

 

@Jul:  I tried this function called from the update state but nothing happens - no error and no movement.

function leaderAttack(){var leader=enemies.getFirstAlive();leader.body.velocity.x-=10;}

Any thoughts?

[j0hnskot]

If nothing happens on both leader.x or leader.body.velocity.x i suspect that something is not working correctly. Try calling console.log(leader) after getFirstAlive(). What's the output?

[JFish]

@j0hnkot I apolgize for this question (I admit to beeing a noob)  ... but I added the console.log(leader) code.  Where am I supposed to see the output?  In the browser?  If so, I see nothing.

[JUL]

use an alert(myStuffhere), instead of console, it's less handy for debugging, but that should do the trick for now

 

Also, (and again), take a close look at the code structure of this example http://examples.phaser.io/_site/view_full.html?d=games&f=invaders.js&t=invaders

 

And spot what fundamentally differs from yours .

 

 

 

 

 

 

 

 

 

var game = new Phaser.Game(800, 600, Phaser.AUTO, 'phaser-example', { preload: preload, create: create, update: update, render: render });

function preload() {

game.load.image('bullet', 'assets/games/invaders/bullet.png');
//etc...

}

var player;
var aliens;
var bullets;
//etc...

function create() {

game.physics.startSystem(Phaser.Physics.ARCADE);

// The scrolling starfield background
starfield = game.add.tileSprite(0, 0, 800, 600, 'starfield');

// Our bullet group
bullets = game.add.group();
bullets.enableBody = true;
bullets.physicsBodyType = Phaser.Physics.ARCADE;
bullets.createMultiple(30, 'bullet');
bullets.setAll('anchor.x', 0.5);
bullets.setAll('anchor.y', 1);
bullets.setAll('outOfBoundsKill', true);
bullets.setAll('checkWorldBounds', true);

// The enemy's bullets
enemyBullets = game.add.group();
enemyBullets.enableBody = true;
enemyBullets.physicsBodyType = Phaser.Physics.ARCADE;
enemyBullets.createMultiple(30, 'enemyBullet');
enemyBullets.setAll('anchor.x', 0.5);
enemyBullets.setAll('anchor.y', 1);
enemyBullets.setAll('outOfBoundsKill', true);
enemyBullets.setAll('checkWorldBounds', true);

// The hero!
player = game.add.sprite(400, 500, 'ship');
player.anchor.setTo(0.5, 0.5);
game.physics.enable(player, Phaser.Physics.ARCADE);

// The baddies!
aliens = game.add.group();
aliens.enableBody = true;
aliens.physicsBodyType = Phaser.Physics.ARCADE;

 

//etc...


}



function update() {

// Scroll the background
starfield.tilePosition.y += 2;

// Reset the player, then check for movement keys
player.body.velocity.setTo(0, 0);

if (cursors.left.isDown)
{
player.body.velocity.x = -200;
}
else if (cursors.right.isDown)
{
player.body.velocity.x = 200;
}

 

//etc...
// Run collision
game.physics.arcade.overlap(bullets, aliens, collisionHandler, null, this);
game.physics.arcade.overlap(enemyBullets, player, enemyHitsPlayer, null, this);

}
 

 

 

 

function collisionHandler (bullet, alien) {

// When a bullet hits an alien we kill them both
bullet.kill();
alien.kill();
//etc..


}

 

 

 

 

function enemyHitsPlayer (player,bullet) {

player.kill();
//etc...

}


 

[JFish]

The alert(console.log(leader)); shows "undefined"

 

The code for the invaders has the whole group moving - which I can do.  This is what the aliesn do - which I believe impacts the entire group.

function descend() {    aliens.y += 10;}

I am wondering how to get the first alien to move some way without moving the others in the group.

[JUL]

Just use alert(leader);

 

Also, what parameters have you passed to the group ?

 

like... myGroup.fixedToCamera or stuffs like that

[JFish]

Okay, now it says "[object Object]" in the alert. 

 

This is how I create the members of the group:

//enemies	enemies=game.add.group();  	enemies.enableBody = true;    enemies.physicsBodyType = Phaser.Physics.ARCADE;   // enemies.createMultiple(30, 'galaga');	for (var i = 0; i < 7; i++)    {         	yellowJacket = enemies.create(game.world.width-40, 75 * i, 'galaga', 'yellowJacket');		yellowJacket.body.gravity.x = horizGravity*-1;    }		for (var i = 0; i < 6; i++)    {         	yellowJacket = enemies.create(game.world.width-90, (75 * i)+100, 'galaga', 'yellowJacket');		yellowJacket.body.gravity.x = horizGravity*-1;    }		for (var i = 0; i < 5; i++)    {         	yellowJacket = enemies.create(game.world.width-140, (75 * i)+125, 'galaga', 'yellowJacket');		yellowJacket.body.gravity.x = horizGravity*-1;    }	    enemies.setAll('anchor.x', 0.5);    enemies.setAll('anchor.y', 1);

[JUL]

yellowJacket.body.gravity.x = horizGravity*-1;

 

 

I think it might come from here...

 

Try something like mySprite.body.velocity.x=horizGravity*2;

[JFish]

horizGravity currently = 0 so that would not do anything ... it is the same as * -1.  I shut off the gravity in favor of trying to move members of the group.  I know that on creation I could do something like this:

body.velocity.x = game.rnd.integerInRange(-200, 200);

to set the individual members in motion.  Now I am trying to call them individually after the creation to move them.  I wanted to start with firstAlive ... but I don't know why it does not work.

 

EDIT: I am trying to do this in the update loop by calling the function

function leaderAttack(){var leader=enemies.getFirstAlive();leader.body.velocity.x-=10;}

The getFirstAlive() seems to be returning an object.  Is the problem that I am constantly calling it before I attempt the move?

 

EDIT 2:  This works to select the first enemy and move it:

enemies.getAt(1).body.velocity.x-=1;

Don't know why getFirstAlive won't do the same thing?

 

EDIT 3: getRandom also works - will eventually move them all since it is in a loop that gets called very frequently (could slow it down with a timer) but it works.

[Heppell08]

I would have used a for iteration loop with that group and moved them like that with some parameters in place for distance/alive etc.

Even a forEach may have done the trick here too.

[JFish]

@Heppell08 - if I understand your post correctly that would be fine for iterating every member of the group to a common action (setAll might work too).  However, I just want to work with individual members of the group without regard to disturbing t he rest of the group.   That is why enemies.getAt(1).body.velocity.x-=1; works to a degree by allowing me to select any one member of the group to move.  That was the thrust of the original post.  However, I still don't understand why group.getFirstAlive().body.velocity.x-=1; does not do the same thing ...

[JUL]

hm.

That's weird... getFirstAlive should work...

 

Maybe you used kill() on them at some point ?

Without using revive(); to resurrect them ?

[JFish]

@JUL ... I am not doing anything yet except for creating everything.  Maybe my syntax is wrong?

enemies.getAt(1).body.velocity.x-=1;  // worksenemies.getFirstAlive().body.velocity.x-=1; // does nothing