It's missing lots... :scruff:
1) I'm not a great teacher, so bear/bare with me..
2)
class Book
...does not create an object. It only defines the parameters & methods of that object type for when it is created.
Since you want to display an image, you also need to define your class 'based on' or 'inheriting from' a class that handles images (bitmaps). This would be the Window or Sprite class. So, your first line should/could be...
class Book < Sprite
3) The 'initialize' method of a class gets executed once when the object is created. It is used to set up default values for the parameters, and define the 'state' that the object is in when it is created. Your test for the switch belongs in an 'update' method.
4)The object that holds the games switches is $game_switches. so your 'if' statement should read:
if $game_switches[1] == true
But, again this belongs in the update method, which you'll see below
5)
$game_system = RPG::Cache.picture("Event1")
$game_system is an existing object with a whole bunch of parameters & methods. The line above overwrites everything in $game_system with an image, and doesn't have any methods to handle images. Images need to be loaded into a Bitmap object, which is a parameter of another object that handles bitmaps (a Sprite or Window).
6) Minor detail, but a good habit. Properly indent your code. It makes it much easier for you & others to read.
class Book
def initialize
if $game_system.switch_id[1] == true
$game_system = RPG::Cache.picture("Event1")
else
return
end
end
end
7) Here is a "Book" class that works. I copied the Sprite_Timer class, and modified it to display your book. I'll do my best to explain it...
#==============================================================================
# ** Sprite_Book
#------------------------------------------------------------------------------
# This sprite is used to display the book.It observes the $game_switches
# class and automatically changes sprite conditions.
#==============================================================================
class Book < Sprite
#--------------------------------------------------------------------------
# * Object Initialization
#--------------------------------------------------------------------------
def initialize
super
self.visible = false
self.bitmap = RPG::Cache.picture("Parchment")
self.x = 320 - self.bitmap.width / 2
self.y = 240 - self.bitmap.height / 2
self.z = 500
update
end
#--------------------------------------------------------------------------
# * Dispose
#--------------------------------------------------------------------------
def dispose
if self.bitmap != nil
self.bitmap.dispose
end
super
end
#--------------------------------------------------------------------------
# * Frame Update
#--------------------------------------------------------------------------
def update
super
if self.visible and $game_switches[1] == false
self.visible = false
end
if self.visible == false and $game_switches[1] == true
self.visible = true
end
end
end
class Spriteset_Map
alias book_init initialize
alias book_dispose dispose
alias book_update update
def initialize
book_init
@book = Book.new
end
def dispose
@book.dispose
book_dispose
end
def update
book_update
if @book != nil
@book.update
end
end
end
class Book < Sprite
This object type inherits properties & methods from the Sprite class. We're saying, "Book is a type of Sprite". The property we're most concerned with is "bitmap", which is another object of the Bitmap class.
def initialize
super
This is the method that gets called when you create a new object of the Book class.
"super" calls the same method in the parent class (Sprite.initialize)
self.visible = false
'visible' is another property of the Sprite class. We want our sprite invisible to start with, so we set it to false.
we use 'self' to say 'this object'. So self.visible is the visible property of the current object.
self.bitmap = RPG::Cache.picture("Parchment")
Now we set the bitmap property (which is it's own object) of the sprite to use the file "Parchment"
self.x = 320 - self.bitmap.width / 2
self.y = 240 - self.bitmap.height / 2
self.z = 500
Set the x & y properties to the upper left corner of the image. (320,240 is the center of the screen). Set the 'z' property so it will be above characters & other map objects.
update
call the update method. Nothing happens in this class, but update also calls 'super', which is the 'update' method of the parent (Sprite).
def dispose
if self.bitmap != nil
self.bitmap.dispose
end
super
end
dispose automatically gets called when the object is destroyed or goes out of scope. Since the bitmap is also an object, we need to dispose it first, then call the dispose method of the parent class using 'super'.
def update
super
if self.visible and $game_switches[1] == false
self.visible = false
end
if self.visible == false and $game_switches[1] == true
self.visible = true
end
end
end
The update method is what we use to check the switch, and change the visibility of the sprite based on the switch setting. We'll call the update method each frame from the same object we use to create the sprite (and dispose it).
'super' calls the update method from the Sprite class.
I used a compound 'if' statement to improve the efficiency. It only changes the visible property if the switch does not agree with the current state of the object (visible or not visible).
class Spriteset_Map
this class already exists, we are just going to add to it. This is the class for all of the images that get created to be used on the map.
We'll use this class to initialize, update, and dispose our "Book" object.
alias book_init initialize
alias book_dispose dispose
alias book_update update
alias is a cool statement we can use to keep an existing class's methods as they are, but add to the beginning or end of that method.
The first alias means, "rename the old 'initialize' method to 'book_init'." so we can create a new initialize method, but still call the old one.
def initialize
book_init
@book = Book.new
end
The 'initialize' method of Spriteset_Map is where we will create the new 'Book' object. First we call the old initialize method (in the Spriteset_Map script) using our alias 'book_init'.
Then we create a new object called @book using our Book class as a template. The .new method of Book creates the object and calls it's initialize method. (which we defined above).
The construct above is the same as inserting the line, "@book = Book.new' at the end of the Spriteset_Map script's initialize method. It's just much neater, easier to keep track of, and allows us to write scripts that we can just "Insert above Main".
def dispose
@book.dispose
book_dispose
end
So, lets do the same thing with the dispose method. This time we'll dispose of our @book object, then call the old 'dispose' method in Spriteset_Map.
def update
book_update
if @book != nil
@book.update
end
end
Same deal with the update method. We call the old 'update' method, then add our update code. Since 'update' gets called from the initialize method in Spriteset_Map, and we are calling 'book_init' before we create our object, our object does not exist the first time 'update' gets called.
So, we add the if statement, "if @book != nil" to prevent an error on that first update. Once the @book object is created, then @book.update can be called.
Does that help?
