Game Development Reference
In-Depth Information
Figure 6-3.
Random point offscreen
In this image, you can see the gray rectangle, which is the same size as the variable
gameSize
. The
dot in the middle is the
CGpoint gameCenter
. The black line going from
gameCenter
to the upper-
left corner of
gameSize
is of the length
distanceFromCenter
. The value of
distanceFromCenter
is
calculated based on the X and Y components of
gameCenter
, using the Pythagorean theorem. Using
gameCenter
and
distanceFromCenter
, we can get a random point on the outer circle by calling
randomPointAround:At
: from the class
Actor
(shown earlier in Listing 6-10).
In Listing 6-13, after calculating the center point and picking a radius of 32, we have to create a
Representation
object to handle the drawing of this power-up. Because we want to use a series of
images to represent power-ups, we create an instance of
ImageRepresentation
called rep and set
the properties backwards and
stepsPerFrame
.
ImageRrepresentation
is passed to
Actor
's
initAt:W
ithRadius:AndRepresentation
: task to set rep as the power-up's representation. Also note that we
set the
Powerup
as the rep's delegate. This means that the instance of
Powerup
we are creating will be
used to specify information about how to draw this actor.
Inspecting
ImageRepresentation
Because we want to separate the game logic regarding an actor and how it is drawn, we are
introducing the class
ImageRepresentation
. This class is responsible for creating the objects
necessary for rendering an actor with a
UIView.
Primarily,
ImageRepresentation
will be created
UIImageViews
with the PNG files in order to draw our actors. Let's take a look at the header of
ImageRepresentation
, shown in Listing 6-14.
