I’m looking at the code below but still not clear about how this hash
forms! The author of a ruby book I read claimed that the code forms
hash. Is it?
#not complete code, if you try to use it, it won’t work!
require ‘yaml’
require ‘wordplay’
class Bot
attr_reader :name
def initialize(options) @name = options[:name] || “Unnamed Bot”
begin @data = YAML.load(File.read(options[:data_file]))
rescue
raise “Can’t load bot data”
end
end
end
So, when you created hash, don’t you have to initialize it with an empty
hash? For example: @name = {}?
Also when I try to use a snippet in irb: @name = options[:name] || “Unnamed Bot”
NameError: undefined local variable or method `options’ for main:Object
from (irb):1
from :0
options is also in File.read(), it’s acting like adding more element to
a hash. Am I right? Though irb tells a different story as if it’s not
how you starting a hash.
Yes, you’d normally create a new has with either Hash.new or hash =
{}. The method above is expecting that an already populated Hash be
passed as its argument (internally referred to as the options
variable). So here’s how you’d use the Bot class:
Also when I try to use a snippet in irb: @name = options[:name] || “Unnamed Bot”
NameError: undefined local variable or method `options’ for main:Object
from (irb):1
from :0
h = {:name => “Joe”, :age => 20}
name = h[:name]
puts name
–output:–
Joe
h = {:age => 30}
name = h[:name] || “Unamed Bot”
puts name
Plus from now on, if something looks like an array but without the index
(ex: options[3]), then I can safely assumed it’s a form of hash but in a
reading stage.
Thank guys!
lists wrote:
On Mar 18, 2009, at 7:50 PM, Power O. wrote:
attr_reader :name
Yes, you’d normally create a new has with either Hash.new or hash =
{}. The method above is expecting that an already populated Hash be
passed as its argument (internally referred to as the options
variable). So here’s how you’d use the Bot class:
def initialize(options) @name = options[:name] || “Unnamed Bot”
begin @data = YAML.load(File.read(options[:data_file]))
rescue
raise “Can’t load bot data”
end
end
end
Not sure what the author was getting at but YAML#load will probably
return a
hash from the data file. The usage of options implies that a hash is
passed
as an argument
So, when you created hash, don’t you have to initialize it with an empty
hash? For example: @name = {}?
@name looks like it’s supposed to be a string which is initialized from
the
options hash, the || notation means that if options[:name] doesn’t exist
then it will default to “Unnamed Bot”.
Also when I try to use a snippet in irb: @name = options[:name] || “Unnamed Bot”
NameError: undefined local variable or method `options’ for main:Object
from (irb):1
from :0
You will need to initialize the hash in this case, or use variables, but
it
might be best if your using irb to use constants such as; @name = “Robocop”
options is also in File.read(), it’s acting like adding more element to
a hash. Am I right? Though irb tells a different story as if it’s not
how you starting a hash.
No it’s not adding elements to the options hash, it is reading them.
That
line returns a hash to @data (which is probably the one you want) based
on
the contents of the file referred to by options[:data_file].
Plus from now on, if something looks like an array but without the
index
(ex: options[3]), then I can safely assumed it’s a form of hash but
in a
reading stage.
Thank guys!
No, you can assume that it is the [] method sent to the object
referenced by options.
Plus from now on, if something looks like an array but without the index
(ex: options[3]), then I can safely assumed it’s a form of hash but in a
reading stage.
Any object can implement its own [] method with whatever semantics it
likes, not just Arrays and Hashes. The [] method is used for lots of
different purposes in the Ruby standard classes:
