Newbie block question

Ruby
1

Hi folks

I’m working on some code that extracts data from a set of XML files
using REXML stores this as arrays of arrays of floats (one array of
floats per file), does some processing and then writes the results to 4
text files for visualisation with gnuplot.

However, what happens is that although 4 files get created all the data
gets saved in the first one to be opened. It’s as if the block in
writeMatrix() stores the reference to the first File object and uses
that on the other 3 method invocations. If that’s the case then I’ve
obviously failed to understand the appropriate way to use a block.

What would be a better way to code this in ruby?

thanks

Dave

Here’s a portion of the class handling writing the files.

class TuneInputData

… snip snip …

def writeData()

writeMatrix(@@LUMINANCE_DATA_FILE, @imageVector)

writeMatrix(@@VOICE_DATA_FILE, @voiceVector)

writeMatrix(@@SOUND_DATA_FILE, @soundVector)

writeMatrix(@@RHYTHM_DATA_FILE, @rhythmVector)

writeColumn(@@COLOURFULNESS_DATA_FILE, @imageColourfulness)

end

def writeMatrix(filename, matrix)

file = File.new(filename, "w")

matrix.each { |row| writeRow(file, row) }

end

def writeRow(file, row)

outString = ""

row.each { |v| outString = outString + v.to_s + " " }

file.puts(outString)

end

… snip snip …

end

2

Dave Snowdon wrote:

that on the other 3 method invocations. If that’s the case then I’ve
obviously failed to understand the appropriate way to use a block.

What would be a better way to code this in ruby?

Hi,

So I took your code, made it look more like Ruby code (snake_case),
simplified it, added example data and ran it. The resulting files were
all as I think they should be. The problem you are having has to lie
somewhere else in your code. Are you shure the class variables
*_DATA_FILE are right, or maybe they all contain the same file name?

Anyway, here’s the code:

class TuneInputData

@@LUMINANCE_DATA_FILE = “luminance.data”
@@VOICE_DATA_FILE = “voice.data”
@@SOUND_DATA_FILE = “sound.data”
@@RHYTHM_DATA_FILE = “rhythm.data”
@@COLOURFULNESS_DATA_FILE = “colourfulness.data”

def initialize
@image_vector = [[1, 2, 3], [3, 2, 1]]
@voice_vector = [[4, 5, 6], [6, 5, 4]]
@sound_vector = [[7, 8, 9], [9, 8, 7]]
@rhythm_vector = [[10, 11, 12], [12, 11, 10]]
end

def write_data
write_matrix(@@LUMINANCE_DATA_FILE, @image_vector)
write_matrix(@@VOICE_DATA_FILE, @voice_vector)
write_matrix(@@SOUND_DATA_FILE, @sound_vector)
write_matrix(@@RHYTHM_DATA_FILE, @rhythm_vector)
# write_column(@@COLOURFULNESS_DATA_FILE, @image_colourfulness)
end

def write_matrix(filename, matrix)
File.open(filename, ‘w’) do |file|
file.puts matrix.collect{ |row| row.join(’ ') }
end
end

end

t = TuneInputData.new
t.write_data

Hope it helped,
Robin

3

Hi Robin

Many thanks for the help - much appreciated. You were right, the problem
was elsewhere - I finally tracked it down to the code reading the data.

Your code to output the data was far more elegant than mine and I’ve
updated my class to match.

I can see I’ll have to kick the camelCase habit too - I guess I’ve spent
too long writing in Java.

thanks

Dave