Creating Spit Spot! (Collisions : SpriteKit : Swift in Xcode) Video Lecture | Swift in Xcode: The Complete iOS Development Guide - App Development

hey what's going on everybody today I'm
going to show you how to create my app
spit-spot
this is part two if you haven't seen
part one be sure to go check it out we
will be mainly focusing on collisions
this time so let's go ahead and get
started alright so first thing we need
to do is open up shooter Xcode project
if you didn't pala part one be sure to
do that right now or else no this will
make sense so let's make this a bit
bigger and today I mentioned that we are
going to work on collisions so the first
thing we need to actually do is right up
here where it says class game scene SK
scene you want to put a comma and then
just type in SK physics ba contact
delegate now inside of this delegate
this is going to pretty much control all
of the contacts that are made between
two different nodes or two different
characters pretty much so what do we
want to happen when things do collide
well let's create a new function down
here and this is actually a function
that's stored inside of the SK physics
contact delegate it is called did begin
contact like so and then inside of this
you have the SK physics contact now if
you want to read more about that you can
always just go over the word and click
on it and find out more about what it is
and where it is but basically what you
need to do is this is going to contain
all of the information that is created
when two objects collide so we need to
go into this information and do things
according to that information that's
created so we need to say let first body
equal and this is going to be contact
dot body a as SK sprite node and then
we're also going to create a second body
so we're going to say let second body
equal contact dot body B and this is
going to be as an SK sprite node as well
and actually this should be contact body
a dot node sorry contact up body a node
and contact body B node and that should
work properly it was giving me an error
originally saying you can't cast from an
SK sprite to an SK sprite node so we
just wanted to grab the node especially
now right now these nodes have no
information so we need to go over to our
small ball and our enemy and we're going
to add some information to it so right
down here in our small ball I'm just
going to say small
ball dot physics body dot category
bitmask and basically what this bitmask
is that you're going to assign a certain
number to the small ball and when this
number collides with a different number
you're going to get information routing
over to the did begin contact so let's
go up here and actually we're going to
create these numbers now these numbers
are kind of special they're they're
pretty much binary numbers that we need
to work with so right up here I'm going
to say struct physics category so we're
going to group all of these characters
that we have the main ball the small
ball and the enemy into a certain
category and inside of this category
we're just going to say static let enemy
equal uint32 just type all that in and
this is going to be equal to zero times
one arrow head arrow head zero so
basically we're just assigning this to a
certain bit number you can look up what
this bit number is yourself but I'm not
going to tell you right now we're just
going to go through all of this since
there's a lot to write so we need to say
static let bullet colon uint32 and this
is going to be equal to zero X 1 dot
arrow arrow 1 and lastly we're going to
have the static let player or basically
we're going to change this name to main
ball colon uint32 and this is going to
be equal to 0 X 1 arrow arrow 2 so now
we're going to assign these numbers to
the certain objects that we want to
create so let's head back over to our
small ball and we're going to say small
ball that physics bodied category
bitmask and this is going to be equal to
our physics category dot bullet and if
you want to make things less confusing
we can actually just change this name up
here and I'm going to change this to the
small ball this is just going to make
things a little bit less confusing for
everyone so we're going to go to the
physics category dot small ball now as
you can see right up here so the small
ball dot physics body data category
bitmask will be equal to the physics
category dot small ball now and now we
also needed to have a collision and
basically what this
is going to do it's going to be small
ball the physics body collision bitmask
and this is going to be equal to the
physics category dot enemy so basically
what we're doing here is we're going to
test a collision to see if we have
collided with the enemy and this will
just allow things to collide with one
another now we need to go down here and
we're going to say small ball dot
physics body dot contact test to bitmask
this is basically going to call this
function if it collides with this
category bitmask that we're going to say
right here so we're going to say dot
contact test bitmask is equal to the
physics category dot enemy so we're
basically going to call this function
and then we're going to test things
accordingly when we actually call that
function and it's only going to call
that function if the small ball physics
body connects with the physics category
enemy now continuing on we want to
assign a name to this ball now this name
will actually be stored into the node
itself versus small ball dot physics
body we need to actually store this name
into the node so we're going to say
small ball dot name will be equal to and
we're going to make this equal to open
quotation mark close quotation mark
small ball and lastly with the physics
we're going to say small ball dot
physics body dynamic and this is going
to be equal to true this is going to
make it be affected by things like
gravity and in case of graduated we need
to say small ball dot physics body dot
affected by gravity and we will set this
to true so we're going to make it as
affected by gravity and it's dynamic
meaning that it's going to be able to
change paths according to what the
environment around it is if it was not
dynamic it would just continue on in a
straight path according to what we have
told it in before and if we said that it
was affected by gravity it would look
very weird and it would not work
properly so that is it for the small
ball now we need to move on to our enemy
so right down here on our enemy I'm just
going to put a comment here and this is
going to be the physics of our enemy so
right inside of this we're going to put
enemy dot physics body dot category
bitmask and this will be equal to the
physics category dot enemy now we need
the enemy dot physics body
to contact test bitmask and we will set
this equal to the physics category dot
small ball and then we also need a
straight line up and down and this
basically means that we're going to be
either hitting the small ball or we're
going to hit the physics category dot
the main ball or the main ball in the
middle so if we hit the small ball or
the main ball we're going to call that
function up there next thing we need to
do is say enemy dot physics body dot
collision bitmask and we're going to
also set this equal to the physics
category dot small ball and the main
ball
I want the enemy to collide with those
other two objects and now with this
enemy we're going to say enemy dot
physics body dynamic and we're going to
set this equal to false we don't want
our enemy to be affected by gravity and
other things so we're going to set that
equal to false and lastly we're going to
add a name so we're going to say enemy
dot to name will be equal to and open
quotation my close quotation mark enemy
all right so let's check out what we
have done so far so let's build and run
and right now there actually is an error
we need to head back over to our project
and we're just going to go to our game
scene dot Swift and go to our did move
to view right here and we need to save
self dot physics world dot contact
delegate we will be equal to self so we
want this view controller itself to
delegate all the contacts that go on and
I just realized that we didn't actually
add inside of this enemies right here we
didn't add a physics body to our enemy
yet so we need to say enemy dot physics
body will be equal to an sk physics body
and then open parentheses and this is
going to be a circle of radius and we're
going to make this equal to the enemy
dot size dot width and now you should
have no errors and this physics body
should be a circle of the radius of the
half of the size of our enemy so now
let's build and run and now as you will
see that we can hit these enemies now
but the problem is you can you can
really see that nothing is happening in
between when we hit them so let's go
over to our contact bit mask that we
created right here this did begin
contact function and we're going to go
over here and we're going to say if our
open parenthesis up in parenthesis first
body dot name
is equal equal to and we're going to
make this equal to the enemy ampersand
ampersand basically meaning if our first
body not name is equal to equal to enemy
and our second body name is equal equal
to and this is going to be equal to a
small ball then close off all those
parentheses or let's say it's the other
way around so we want to have two
straight lines like so and then we're
going to have more parenthesis we're
going to say first body dot name is
equal equal to and this is going to be
equal to the small ball ampersand
ampersand open parenthesis the second
body dot name is equal equal to the
enemy so basically it's just this first
part flipped around so we're checking
for both instances checking to make sure
the first body or the second body is
equal to enemy or the first body or the
second body is equal to the small ball
and now with this information we're
going to do something so close it off
with your two parentheses and then we're
going to have an open curly bracket
enter close curly bracket and now what
do we want to do well first off we want
to call another function so let's create
a new function right down here and we're
going to call this the collision bullet
so we're going to basically this is what
happens when we collide with a bullet or
with the small ball so right inside of
this collision bullet we need to go open
parenthesis and this is going to be our
enemy then colon and this is going to be
equal to an S case sprite node comma and
we're also creating another variable
called our small ball and then this is
going to be this colon s case sprite
note as well and basically what this is
gonna do we're going to take these first
bodies and we're going to apply them to
this collision bullet now because all of
these small balls are not created
publicly we have to do this workaround
so we need to go into our did begin
contact and we're basically assigning
all of these to these variables in here
and now we're going to do things with
those variables so right after the small
ball we're going to say open curly
bracket enter close curly bracket and
what do we want to happen well first
thing we need to do is we're going to
say enemy dot physics body dot dynamic
and we're going to set this equal to
true now we want it to be affected by
gravity so now we're also going to say
enemy
physics body dot affected by gravity and
we're going to make this equal to true
as well and the next thing we need to do
is actually change the mass of our enemy
and our ball so we're going to say enemy
dot physics body dot mass will be equal
to and this is going to be equal to I'm
just going to set it to a nice five this
will make it drop fast so we're going to
make it go off the screen pretty fast so
we can continue on with our gameplay and
we also need to do this with our ball so
we're going to say small ball dot
physics body dot mass will be equal to
and we're going to make this equal to
five as well and now if we go up here to
our did begin contact again we can go
inside of this if statement and we want
to call this function that we created so
we're going to type in collision bullet
and now it's expecting two different
variables so now we want to apply these
sprite nodes that we have and we're
going to apply them to what we just
created now the way I've actually
programmed this is a little bit
incorrect so we're going to actually add
an else if statement right over here and
we're going to take this second part
right up here and we're going to apply
that right into this else if statement
we're going to take out those two dashed
lines and we are also going to take out
that second part of the function right
up there now we're also going to fix the
parentheses just to make sure
everything's lined up properly and then
after this else if statement we're going
to add an open curly bracket enter close
curly bracket now looks like I have no
errors so basically in this collision
bullet right here we're going to apply
say if the first body dot name is equal
to equal to enemy then we want to set
the our enemy equal to our Cesc a sprite
node so we're going to say the collision
Boland and our enemy will be equal to
our first body like so and our small
ball will be equal to our second body
now in the other case then we want to
say collision bullet and we're going to
apply the enemy to our second body and
the small ball we're going to apply this
to our first body it's a little bit of a
weird workaround but it works so now
we're going to build and run this and
this is just going to first let us know
that we have any errors so build and run
now I'm protecting my community I'm
hitting them all sorts of stuff good
good and now one thing you will notice
is that these balls are still coming so
the problem with this is you
we go into our collision bullet right
now we need to actually remove all the
actions from our enemy because it's
still trying to move to the center
position of our scene so we're going to
say enemy dot remove all actions and
we're also going to do this with our
ball so we're going to save small ball
dot to remove all actions it doesn't
really have any actions but we're going
to do it just for safekeeping so now
it's building run and now as you can see
I can hit the ball in midair and it's
going to defend my now one thing you
will notice is that our main ball in the
center is actually not being collided
with at all so we actually need to head
back and we're going to add some physics
to our main ball so first thing we need
to say is main ball dot physics body
will be equal to and this is going to be
equal to an SK physics body open
parenthesis and this is going to be a
circle of radius and this radius will be
equal to our main ball dot size dot
width divided by two and then we're
going to apply a category bit mask to
our ball so I'm just going to say main
ball dot physics body dot category bit
mask and we're going to make this equal
to our physics category dot main ball
and then we're going to add a main ball
dot physics body collision bit mask and
we're going to make this equal to
physics
category dot enemy so when it collides
with the enemy it's going to be a
collision and we will notice that and we
also want to contact test base masks so
we're going to say main ball dot physics
body contact Test bit mask and this is
going to be equal to a physics category
dot enemy so we're going to call the
function that did begin contact function
when we collide with the enemy and now
speaking of which let's head into our
did begin contact and we're just going
to add an if statement for our main
balls will add more into the scoring
later on but right now we're actually
just going to test and make sure that it
is colliding properly so let's say else
if and let's just copy and paste what we
have right up here and just replace some
names so we're going to go up here and
we're going to say else if the first
body dot name is equal to the main ball
and the second body dot name is equal to
equal to enemy and we can also just grab
this first part up here for the other
else if statement
but right after this if statement we
need to add a curly bracket then we need
to type in else and then we're going to
paste what we what I just said and like
I said we're not going to deal with any
functions right now but we will in part
3 right now let's go ahead and just type
in NS log and this is going to be high
if it hits the main ball and we're going
to do this with the other one so this
will be high and also I forgot to
mention that we need to go inside of
this if-elsif statement right here and
we're also going to change this to the
main ball and this should actually be NS
log hello and now if we were to build
and run this now as you just saw our
main ball just flew off the screen so we
need to head back over to our did move
to view and go over to our main ball and
I'm just going to say main ball physics
body dot affected by gravity I'm going
to set this equal to false we do not
want it to be affected by a gravity in
any way and we need to have the main
ball dot physics body dot dynamic equal
to false as well and I also forgot to
add the name to our physics body so we
need to say main ball dot name will be
equal to and this is going to be equal
to main ball now one thing you will
notice is that as these enemies are
coming in right now we're not getting
any output but as soon as we start
shooting the ball we actually do get
some output that says hi your hello but
this should all be fixed in part three
where we work on actually scoring and
other things so on to part three thank
you all so much for watching if you
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think it's again and I will see you in
the next one