Ruby Case Statements with Multiple conditions - ruby-on-rails

Question

I have a method that returns image size based upon the users selection and now I want to add another condition to my case statement. It is not setting the correct image size when I call the method again after my system call doing pdfinfo if the user chose STANDARD it should be 1250x1075 but it does not even do my case statement, it directly goes to else and sets 1728x1075
This is what I've tried
205 def FaxCall.set_image_size(resolution, pdf_size=nil)
206 case resolution
207 when STANDARD && (pdf_size != LEGAL_PDF_SIZE)]
208 image="1728x1075"
209 when FINE && pdf_size != LEGAL_PDF_SIZE
210 image="1728x2150"
211 when SUPERFINE && pdf_size != LEGAL_PDF_SIZE
212 image="1728x4300"
213 when [STANDARD, (pdf_size === LEGAL_PDF_SIZE)]
214 image="1250x1720"
215 when FINE && pdf_size == LEGAL_PDF_SIZE
216 image="1700x2800"
217 when SUPERFINE && pdf_size == LEGAL_PDF_SIZE
218 image="3400x5572"
219 else
220 image="1728x1075"
221 end
222 return image
223 end
This is where I call my method
135 def FaxCall.prepare_doc(in_file,out_file,res=STANDARD)
139 image = FaxCall.set_image_size(res)
140 res = STANDARD unless RESOLUTION_OPTIONS.values.include?(res)
145 if ext.eql?("pdf")
146 pdf_size = `pdfinfo "#{in_file}" | grep 'Page size:'`.gsub(/Page size:\s*\b/, '').chomp
147 if pdf_size == LEGAL_PDF_SIZE
148 image = FaxCall.set_image_size(res,pdf_size)

Answer 1

STANDARD && (pdf_size != LEGAL_PDF_SIZE), FINE && pdf_size != LEGAL_PDF_SIZE, SUPERFINE && pdf_size != LEGAL_PDF_SIZE, FINE && pdf_size == LEGAL_PDF_SIZE, and SUPERFINE && pdf_size == LEGAL_PDF_SIZE are all booleans, but resolution is a String, so they will never match.
[STANDARD, (pdf_size === LEGAL_PDF_SIZE)] is an Array. An Array will never match a String.
So, therefore, none of your cases will ever match, and you will always fall into the else case.

Answer 2

I'd create an array of hashes...
RES_MAP = [{res: STANDARD, legal: false, image: "1728x1075"},
{res: FINE, legal: false , image: "1728x2150"},
{res: SUPERFINE, legal: false , image: "1728x4300"},
{res: STANDARD, legal: true, image: "1250x1720"},
{res: FINE, legal: true , image: "1700x2800"},
{res: SUPERFINE, legal: true , image: "3400x5572"}]
and then change FaxCall.set_image_size(resolution, pdf_size=nil) to look up the matching hash and grab the image size.
def FaxCall.set_image_size(resolution, pdf_size)
is_legal = (pdf_size == LEGAL_PDF_SIZE)
match_res = RES_MAP.select{ |r| r[:res] == resolution && r[:legal] == is_legal}.first
return match_res.present? : match_res[:image] ? "1728x1075"
end
Easier to read and to add both more map values and extra criteria.

Answer 3

That's because STANDARD and ELSE have the same image size.
207 when STANDARD && (pdf_size != LEGAL_PDF_SIZE)]
208 image="1728x1075"
219 else
220 image="1728x1075"
See what I mean ?

Answer 4

#Jörg has explained the problem with your code. You might consider writing your method as follows.
DEFAULT_IMAGE_SIZE = "1728x1075"
def FaxCall.set_image_size(resolution, pdf_size=nil)
case pdf_size
when LEGAL_PDF_SIZE
case resolution
when STANDARD then "1250x1720"
when FINE then "1700x2800"
when SUPERFINE then "3400x5572"
else DEFAULT_IMAGE_SIZE
end
else
case resolution
when STANDARD then "1728x1075"
when FINE then "1728x2150"
when SUPERFINE then "1728x4300"
else DEFAULT_IMAGE_SIZE
end
end
end