Im beginning work with Cocos2d and have been working off this tutorial (link is for part 9) the past few days.
In reading the source and trying to understand it I have reached a section that doesnt make any sense to me.
-(void)gameLogic:(ccTime)dt {
static double lastTimeTargetAdded =0;
double now = [[NSDate date] timeIntervalSince1970];
AppDelegate *delegate = [[UIApplication sharedApplication] delegate];
if(lastTimeTargetAdded == 0 || now - lastTimeTargetAdded >= delegate.curLevel.spawnRate) {
[self addTarget];
lastTimeTargetAdded = now;
}
}
called via this:
[self schedule:#selector(gameLogic:) interval:0.2];
With the fact that lastTimeTargetAdded is created and set each time the function runs how is it ever not 0? And if thats the case what is the point of lastTimeTargetAdded = now? With the if statement being an OR (||) it never evaluates the other side of it so why is that even there?
I understand well enough what the function does just not so much how it does it. This method is suppose to spawn creeps based on their spawn rate. Making sure all the creeps in the wave arent just dumped on screen. And the method does do that well enough.
it is a static var ... the first statement sets to 0 only on the first invocation of gameLogic. On each subsequent invocation, lastTimeTargetAdded has the value that was set in the previous invocation.
Related
I have issues with Google app script IF condition.
Problem i am facing its not returning value TRUE rather going to next/ Else statements.
Code i am having:
const numberOfRowsToUpdate = deliveryDate.length;
// For each item making the for loop to work
for (i=0 ; i < numberOfRowsToUpdate;i++) {
debugger;
var dp = depositAmount[i];
if(dp!==""|| dp!==0 || dp !==null || dp!==isblank())
{ .... <statements>
}
}
I want to check whether particular cell of the array is empty / zero / returning null value.
thanks in advance for the help.
SUGGESTION
I have used a similar script I'm using for a spreadsheet in which I need to search through every row for some data, but obviously adpating it to your case, and since I don't have your full code (and still can't comment asking for more info due to my recent joining in SO), I had to simplify it, in hope it will work for you.
What I did was use your incrementing i index from the for loop and use it to scan every row, while adjusting it to fit your array index, because we can't have i = 0 as a row index, and it would skip the first value on the array if left as i = 1).
SCRIPT
function test(){
const n = 6;
var depositAmount = [7,2,0,2,0,8];
// For each item making the for loop to work
var ss = SpreadsheetApp.getActive();
Logger.log(ss.getName());
for (var i=1 ; i <= n ;i++) {
debugger;
ss.getRange("A"+i).setValue(1);
var dp = depositAmount[i-1];
Logger.log(dp)
if(dp != "" || dp != 0 /*|| dp != null || dp != isblank()*/)
{
ss.getRange("B"+i).setValue(dp);
}
else
{
ss.getRange("C"+i).setValue("VOID")
Logger.log(i-1+"th index of array is "+ss.getRange("C"+i).getValue());
}
}
};
RESULTS
After running it with the four original conditions you used, i didn't get the expected result, as you must have, leading to this:
.
While studying your original code, I stumbled upon this question about the differences between == and ===, as well as != and !==.
So before I used this in our favor, I tried the old trial and error method, using only one condition at a time, and then stacking them up. Not only I managed to find out the !== operator didn't work properly for this case, but also the comparison with null and the isblank() function (at least in my case, because i haven't defined it, and I'm not sure it is a built-in function) also don't work with either operator.
Therefore, using the != operator helps you better than the strict !==.
The result of the final script is that:
.
NOTES
I also tried using a null value within the array ([7,2,0,2,,8]), but it would always break away from the loop, never scanning the whole array, and I don't know how to circle that.
Here is the Execution Log for this script:
EDIT
While fooling around, I found this question and the answer by Etienne de Villers might be even faster to apply, or at least more useful for your purposes.
I know the title may seem fairly confusing, was just unsure on how to ask this...
So, I'm working on a basic sample game (not going to be a complete game or anything), where you can move around and are chased by an enemy character that attacks you. The problem is that when the attack function is called, instead of only removing one heart/hitpoint, they continue to be 'spam removed'. Here's what I'm working with...
void Enemy::attackPlayer()
{
if (distance < 50)
{
Player::health--;
return;
}
}
Pretty simple, right? Well the problem is that I need some way of I guess 'sleeping' the single function so that instead of continuing to remove health, it stops after one, then after let's say, 3 seconds, allows another attack to occur.
I think you can create two global time variables that are passed to your attack function. startTime is initiated once you call your attack function (outside). endTime is initiated right after removing one health from player (inside your function). Then you simply add a if statement before the distance if statement to check the delta time between these two and if they are more than 3 seconds then do the rest to remove another health.
You could probably have the Enemy class contain a method like:
bool canAttack(){
if(attackTimer >= 3000){
attackTimer = 0;
return true;
}
return false;
}
Then you could modify your damage condition to be something like:
if (distance < 50 && canAttack())
Of course, you would have to add a timer to the Enemy class and have it start and stop based on proximity to the player.
I'm sure there is a better way to handle this--also, this depends a bit on the implementation of the rest of your code. If you are using something like SFML, there is a built-in event system that would make this a bit easier to handle. Hopefully this helps a bit!
After taking some of the answers you guys gave me into consideration and messing around with some things by myself, I've came up with a pretty simple solution:
int Enemy::attackTime = 0;
And then...
void Enemy::attackPlayer()
{
if (distance > 60)
return;
if (time(0) > attackTime)
{
attackTime = time(0) + 3;
Player::health--;
}
}
I guess, player won't get another attacked from any enemy for 3 seconds. However, enemy can attack to another player if exist. Thus, this timer variable is keep into Player class. If I am correct, I think this code will work.
class Player
{
private:
uint32_t last_attack_timer;
...
public:
void set_last_attack_timer(uint32_t timer){this->last_attack_timer = timer;};
uint32_t get_last_attack_timer(void){return last_attack_timer;};
...
}
void Enemy::attackPlayer()
{
uint32_t timer = time(0);
if (distance < 50 && timer-Player::get_last_attack_timer>3000)
{
Player::health--;
Player::set_last_attack_timer(timer(0));
return;
}
}
I am working on one game in cocos2d-x (iOS). There I have created few scenes and did transitions in between those scenes. During each transition init() of each scene(layer) is called (Also constructor is called each time before init()). My question is, How can I make ONLY ONE time initialisation of my variable inside this init() or constructor, even when init() is called each time? Or any OTHER alternative solution for the same?
CCUserDefault::sharedUserDefault()->setBoolForKey("firstTimeInit", false);
bool firstTimeInit = CCUserDefault::sharedUserDefault()->getBoolForKey("firstTimeInit");
if (!firstTimeInit)
{
for(int i = 0; i < 10; i++)
{
char szName[22] = {0};
sprintf(szName, "Rank%i", i);
CCUserDefault::sharedUserDefault()->setIntegerForKey(szName,0);
CCUserDefault::sharedUserDefault()->flush();
int score = CCUserDefault::sharedUserDefault()->getIntegerForKey(szName);
vScore.push_back(score);
}
CCUserDefault::sharedUserDefault()->setBoolForKey("firstTimeInit",true); }
I wrote this code inside init() method.. and I want that firstTimeInit which I made false, initialise only once.
EDIT #####
In cocos2d-x for every transition init() method is called that is why every time our initialisation takes place. Also I want this one time initialisation even after I quit my game and rerun. I tried it by using CCUserDefault's setBoolForKey() but in vain,as it is also in init().
This will do what you are after
bool val = cocos2d::CCUserDefault::sharedUserDefault()->getBoolForKey("initialized");
if (val != true){
cocos2d::CCUserDefault::sharedUserDefault()->setBoolForKey("initialized", true);
cocos2d::CCLog(" initializing value ");
}
currently whats happening :-
1>game starts you put firstTimeInit=false, which makes the if condition true;
2>then you assign firstTimeInit=true in the end.
3> you quit and game starts again and runs step 1 ,which will override present value in firstTimeInit from true to false,again making the if condition true so you need to remove first statement
CCUserDefault::sharedUserDefault()->setBoolForKey("firstTimeInit", false);
so that once the key is set to true it is never set to false;
Assumption:But I am assuming if a boolean key is not present then getting its value always returns false. Checked several times , and it returned false.
I know that in order to kill invaders in C++, I need to make a collider.
However, nothing will ever kill the invaders in that game.
Here's the code in the header:
bool DoCollision(float Xbpos, float Ybpos, int BulWidth, int BulHeight, float Xipos, float Yipos, int InvWidth, int InvHeight);
This is the function I'm initializing:
bool Game::DoCollision(float Xbpos, float Ybpos, int BulWidth, int BulHeight, float Xipos, float Yipos, int InvWidth, int InvHeight) {
if (Xbpos+BulWidth < Xipos || Xbpos > Xipos+InvWidth) return false;
if (Ybpos+BulHeight < Yipos || Ybpos > Yipos+InvHeight) return false;
return true;
}
And this is what happens if somebody presses the space key:
if (code == 57) { //Space
myKeyInvader.MeBullet.Active = true;
myKeyInvader.MeBullet.Xpos = myKeyInvader.Xpos + 10;
myKeyInvader.MeBullet.Ypos = myKeyInvader.Ypos - 10;
myKeyInvader.MeBullet.yvuel = 0.2;
myKeyInvader.MeBullet.BulletP->CopyTo(m_Screen,myKeyInvader.Xpos,myKeyInvader.Ypos);
if (DoCollision(Invaders[counter].MyBullet.Xbpos,Invaders[counter].MyBullet.Ybpos,Invaders[counter].MyBullet.BulWidth,
Invaders[counter].MyBullet.BulHeight,Invaders[counter].Xipos,Invaders[counter].Yipos,Invaders[counter].InvWidth,Invaders[counter].InvHeight)) {
//myKeyInvader.Ypos = 100;
Invaders[counter].Active = false;
printf("Collide!\n");
}
}
Does anybody know what's going wrong?
The problem isn't C++. The problem is how you are using it. The only way you'll get a kill with your code as written is if the invader is right on top of you. But that's too late. The alien invader has already killed you.
What you need to do is make those bullets into objects that you propagate over time, just like your invaders are objects that you propagate over time. The response to the user pressing a space key should be to add a new instance of a bullet to the set of active bullets. Each of those active bullets has a position that changes with time. On each time step, you should advance the states of the active invaders per the rules that dictate how invaders move and advance the states of the active bullets per the rules that dictate how bullets move. Remove bullets when they reach the top of the screen, and if an alien invader reaches the bottom of the screen, game over.
After propagating, removing off-screen bullets, and checking for game over, you want to check for collisions between each of the N bullets with each of the M invaders. When a collision is detected, remove the bullet from the set of active bullets and delete the alien invader from the set of active invaders. And of course you'll want some nifty graphics to show the user that another alien bit the dust.
Aside: Being an NxM problem, this check might be the biggest drain on CPU usage. You can speed this up with some simple heuristics.
You could manage the collections of alien invaders and bullets yourself, carefully using new and delete so as to prevent your invaders and bullets from killing your program with a memory leak. You don't have to do this. C++ gives you some nifty tools to manage these collections. Use one of the C++ standard library collections instead of rolling your own collection. For example, std::vector<AlienInvader> invaders; or std::list<AlienInvader> invaders, and the same for bullets. You'll be deleting from the middle a lot, which suggests that std::list or std::deque might be more appropriate than std::vector here.
You test the collision for the fired item just when they are created
Shouldn't be the test collision done in the main loop for each existing item at each frame ?
Don't worry, C++ has got all you need to kill invaders :)))
It's not easy to give advice based on so little code, but here the only logical error seems to be you test for collision only when space is pressed; you should test for it in an outside loop probably:
if (code == 57) { //Space
myKeyInvader.MeBullet.Active = true;
myKeyInvader.MeBullet.Xpos = myKeyInvader.Xpos + 10;
myKeyInvader.MeBullet.Ypos = myKeyInvader.Ypos - 10;
myKeyInvader.MeBullet.yvuel = 0.2;
myKeyInvader.MeBullet.BulletP->CopyTo(m_Screen,myKeyInvader.Xpos,myKeyInvader.Ypos);
}
From a logical point of view, pressing Space should fire a bullet: the starting position for the bullet is set, and so is its speed on the Y axis (so that it goes up).
The code that check for collision should go outside of this if block. In fact, this block of code is executed only if you're still pressing space -that is: still firing-. Should collision be checked only if you're "still firing"? Do the fact that you fired a bullet and started waiting for it to destroy the invader interfere in some way with the fact that this bullet can reach the invader and, indeed, destroy it? Of course not!
if (DoCollision(Invaders[counter].MyBullet.Xbpos,Invaders[counter].MyBullet.Ybpos,Invaders[counter].MyBullet.BulWidth,
Invaders[counter].MyBullet.BulHeight,Invaders[counter].Xipos,Invaders[counter].Yipos,Invaders[counter].InvWidth,Invaders[counter].InvHeight)) {
//myKeyInvader.Ypos = 100;
Invaders[counter].Active = false;
printf("Collide!\n");
}
You want collision to be checked in an outside loop, the same that probably also contains the checks for key presses. In this way, even if you're just looking at the screen and waiting, the program keeps testing the condition and, when it's fulfilled, code associated with the event of collision is executed (that is: an invader is "inactivated").
You say //Space , is that what it is or should it be 32 (if ASCII) instead of 57? Does the program flow into the if==57 block?
Your code looks fine, but you need two loops around the collision checker: one for checking all invaders (not just one of them) and another one to check at every bullet position along its trajectory, not just the moment when it leaves the gun.
I will assume we have an auxiliary function that moves the bullet and returns whether it is still inside the screen:
bool BulletIsInScreen();
Then we can write the loops:
if (code == 57) { // Space
while (BulletIsInScreen()) {
for (size_t i = 0; i < counter; ++i) { // counter is the number of invaders,
// according to your comment to your own answer
myKeyInvader.MeBullet.Active = true;
myKeyInvader.MeBullet.Xpos = myKeyInvader.Xpos + 10;
myKeyInvader.MeBullet.Ypos = myKeyInvader.Ypos - 10;
myKeyInvader.MeBullet.yvuel = 0.2;
myKeyInvader.MeBullet.BulletP->CopyTo(m_Screen,myKeyInvader.Xpos,myKeyInvader.Ypos);
if (DoCollision(Invaders[i].MyBullet.Xbpos, Invaders[i].MyBullet.Ybpos,
Invaders[i].MyBullet.BulWidth, Invaders[i].MyBullet.BulHeight,
Invaders[i].Xipos, Invaders[i].Yipos,
Invaders[i].InvWidth, Invaders[i].InvHeight)) {
//myKeyInvader.Ypos = 100;
Invaders[i].Active = false;
printf("Collide!\n");
}
}
}
}
Now this should work as expected.
Hello I am trying to get enemies to move left and right as if they are sliding backwards and forwards I know this can be done with the following code:
slide += slide_incr;
if(abs(slide)>30) slide_incr = -slide_incr;
However this is of no use to me as I need to set a boolean so I can cycle through the frames for when the enemy is going right or going left.
Ive tried the follow code with no luck:
if(abs(eSlide)<=0)
{
eSlide += eSlide_incr;
}
if(abs(eSlide)>30)
{
eSlide_incr = -eSlide_incr;
}
Any ideas on how I can implement it?
Thanks
You want to hold a hysteresis state for if you're sliding forward or backward. You are also mixing up how to use the abs() function when bounds checking. Try something along the lines of:
eSlide += eSlide_incr;
if (abs(eSlide) >= 30) {
eSlide_incr = -eSlide_incr;
}
the first thing that stands out for me is that the contents of the block:
if (abs(eSlid) <= 0) {
eSlide += eSlide_incr;
}
will never ever run (the absolute value will always be greater than or equal to 0)
as for your boolean facing, that can be achieved with:
bool isSlidingRight = eSlide_incr > 0;
(note: this would still use the left animation set for values of 0)