I am not a ruby expert and this is giving me trouble. But how Would I go about creating an array of objects/classes in ruby? How would initialize it/declare it? Thanks in advance for the help.
This is my class, and I want to create an array of it:
class DVD
attr_accessor :title, :category, :runTime, :year, :price
def initialize()
@title = title
@category = category
@runTime = runTime
@year = year
@price = price
end
end
Ruby is duck typed (dynamic typing) And almost everything is an object, so you can just add any object to an array. For example:
[DVD.new, DVD.new]
will create an array with 2 DVDs in it.
a = []
a << DVD.new
will add the DVD to the array. Check the Ruby API for the full list of array functions.
Btw, if you want to keep a list of all the DVD instances in the DVD class you can do this with a class variable, and add it to that array when you create a new DVD object.
class DVD
@@array = Array.new
attr_accessor :title, :category, :runTime, :year, :price
def self.all_instances
@@array
end
def initialize()
@title = title
@category = category
@runTime = runTime
@year = year
@price = price
@@array << self
end
end
now if you do
DVD.new
you can get the list of all the DVDs you have created so far:
DVD.all_instances
def f █ block; end; f {}. Which returns, well, an object.
two_DVD = Array.new(2){DVD.new}
In order to create an array of objects in Ruby:
Create the array and bind it to a name:
array = []
Add your objects to it:
array << DVD.new << DVD.new
You can add any object to an array, at any time.
If you wish to have access to every instance of the DVD class, then you can rely on ObjectSpace:
class << DVD
def all
ObjectSpace.each_object(self).entries
end
end
dvds = DVD.all
By the way, the instance variables are not being initialized correctly.
The following method call:
attr_accessor :title, :category, :run_time, :year, :price
Automatically creates attribute/attribute= instance methods to get and set the value of the instance variables.
The initialize method, as defined:
def initialize
@title = title
@category = category
@run_time = run_time
@year = year
@price = price
end
Sets the instance variables, despite taking no arguments. What effectively happens is:
attribute reader method is callednilnil becomes the value of the variableWhat you want to do is pass the values of the variables to the initialize method:
def initialize(title, category, run_time, year, price)
# local variables shadow the reader methods
@title = title
@category = category
@run_time = run_time
@year = year
@price = price
end
DVD.new 'Title', :action, 90, 2006, 19.99
Also, if the only required attribute is the DVD's title then you can do it this way:
def initialize(title, attributes = {})
@title = title
@category = attributes[:category]
@run_time = attributes[:run_time]
@year = attributes[:year]
@price = attributes[:price]
end
DVD.new 'Second'
DVD.new 'Third', price: 29.99, year: 2011
