ruby: validate input before appending to array

Question

I have a ruby class that has an Array as one of its instance variables. I'm trying to figure out how to validate data that is being pushed onto the array.

class Something
  def things
    @things ||= Array.new
  end
end

So I can declare an instance and add stuff to the array pretty easily this way.

@s = Something.new
@s.things << "one"
@s.things << "two"

I tried to create a class method named things<<(inString) to handle the validation but that is not valid syntax. So what approach can I take?

Josué Lima · Accepted Answer · 2015-04-27 03:15:46Z

1

Try something like:

things << data if valid?(data)

where valid? is your validation method.

Example:

...
# will push only when quantity is greater than 0
def push(quantity)
  things << item if valid?(quantity)
end

private
  def valid?(number)
    number > 0
  end

If you want to have you own ThingsArray just create an Array subclass and override the push (<<) method to make the validation before pushing:

class ThingsArray < Array
  def << (item)
    return unless valid?(item)
    super
  end

  private

  def valid?(item)
    item > 0
  end
end

class Something
  def things
    @things ||= ThingsArray.new
  end
end

edited Apr 27, 2015 at 3:15

answered Apr 27, 2015 at 2:50

Josué Lima

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Comments

hawk · Accepted Answer · 2015-04-27 03:16:06Z

0

How about this?

class MyThings < Array
  def << (item)
    # do your validation with item
    self.push(item) if item.valid?
  end
end

class Something
  def things(item)
    @things ||= MyThings.new
  end
end

edited Apr 27, 2015 at 3:16

answered Apr 27, 2015 at 3:02

hawk

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