Ruby

Ruby - passing hash argument, but accept it as Array

Dear Ruby experts,

I create a new method with accepting one argument.
In other class, I pass a Hash as the argument, but somehow it was read as Array inside the method.
Any suggestion or advice?
Thanks.

# calling resize method
      args = {}
      args[:max] = 200
      logger.error("args.class = #{args.class}") #return args.class = Hash
      image = Picture.resize args
 
# resize method
  def Picture.resize *args 
    logger.error("Picture resize args.class = #{args.class}") #return Picture resize args.class = Array
    logger.error("Picture resize args = #{args}") #return Picture resize args = max200
    max= (args[:max] == nil)? 350 : args[:max] #return TypeError Symbol as array index

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# first reworking of your resize method def Picture.resize(new_max=350) max = new_max end # this sets image to have 'max' = 350 image = Picture.resize # this sets image to have 'max' = 200 image = Picture.resize 200 # another reworking def Picture.resize(new_max=350, *extra_args) max = new_max picture_args = extra_args # or unless extra_args.empty? unless extra_args[0].nil? first_extra = extra_args[0] end unless extra_args[1].nil? second_extra = extra_args[1] end end end

I think I understood, but I probably didn't phrase my answer correctly. Partly, it is because I can see that you are trying to have 'args[:max]' default to 350, so I figured I'd separate that out to help illustrate that. It also appears that you've changed what Picture.resize is expecting, since you had 'image' being set to the results from Picture.resize before.

In any case, the ability to set a default value for an argument is not limited to integers. You can set the value to be an instance of any object available: Hash, Array, Float, String, Foobar (if a Foobar class has been defined), etc. So if you want, you can set the arguments to an empty hash, or a hash with specific key/value pairs already populated. See below.

I've reimplemented your original Picture.resize example, such that the argument to resize is optional, but it still works as you expected. However, I added the check that 'args' is a Hash; otherwise, if something other than a hash is passed to resize, the method would blow up when the 'has_key?' would be attempted against 'args'.

With all that said, you can just as well use the * notation you used in your last comment. Of course, based on what I see, you've now make the first argument passed to 'resize' required, because it is assigned to image; no check for whether it's there or not.

# default args to an empty hash
def Picture.resize( args={} )
 ...
end
 
# default args to a has with :max set to 350
def Picture.resize( args={:max => 350} )
  ...
end
 
# alternate implementation of your original Picture.resize example
def Picture.resize( args={} )
  unless args.is_a?(Hash)
    raise ArgumentError, 'Picture.resize expects a Hash to be passed, or no argument at all'
  end
  unless args.has_key?(:max)
    args.merge!({:max => 350})
  end
  logger.error("Picture resize args.class = #{args.class}") #return Picture resize args.class = Array
  logger.error("Picture resize args = #{args}") #return Picture resize args = max200
  max = args[:max]
end

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Ruby - passing hash argument, but accept it as Array

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