CODEWITHSUNDEEP
rubyparametersinitialization
Rich_F
Rich_F

Reputation: 2056

Ruby Object Initialize with Optional Arguments

How can I code an initalizer() method to form instance variables (empty or otherwise), then iterate through a set of args to set instance variables?

This is what I am thinking:

def initialize(*p)
  @sid                      = "123asdf654"
  @token                    = "abc123"
  @bert                     = "1192875119"
  @me                       = "4165551212"
  @media_url                = ""
  @message                  = ""

  args.each do |k,v|
    instance_variable_set("@#{k}", v) unless v.nil?
  end
end

I want to have the ability to set known instance variables (shown here), then iterate through args and either update the values of chosen instance variables, or create new ones.

Upvotes: 2

Views: 6728

Answers (1)

tadman
tadman

Reputation: 211610

If you're going to do that you need to accept not an array of arguments (varargs style) like you've specified, but either an options hash or the new keyword-args style option.

The classic approach:

def initialize(attributes = nil)
  attributes and attributes.each do |k,v|
    instance_variable_set("@#{k}", v) unless v.nil?
  end
end

The new keyword-arguments approach:

def initialize(**options)
  options.each do |k,v|
    instance_variable_set("@#{k}", v) unless v.nil?
  end
end

You can also subclass OpenStruct to get behaviour like this for free.

Keep in mind there's a new option style that might be a good mix of both these approaches:

def initialize(sid: '123', token: '...', ...)
  @sid = sid
  @token = token
  # ...
end

You can specify defaults for the named keyword arguments.

Upvotes: 5

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