Rake question - loops and tasks

Hi,
I have a general question regarding rake:

Say I have a list of files (based on file extension), that all need to
be processed in the same way. The output of this processing is required
by a downstream task. How do I run this in rake?

My approach was:

my_files.each do |file|

target_file = ‘#{file}.transformed’
file target_file => file do

transform here

end

task :transform => target_file
end

next_file = ‘transformed_files.txt’
file next_file => :transform do

Do something with all transformed files to produce 1 output file

end

And this fails, complaining that it does not know how to build
:transform

Is this a syntactic issue? The workflow above correctly iterates over
the input files, creates transformed files and then complains that it
doesn’t know how to build :transform. I am at a loss…
Any ‘better’ ways of doing this?

On 07/12/11 09:46 , Marc H. wrote:

Do something with all transformed files to produce 1 output file

end

And this fails, complaining that it does not know how to build
:transform

Is this a syntactic issue? The workflow above correctly iterates over
the input files, creates transformed files and then complains that it
doesn’t know how to build :transform. I am at a loss…
Any ‘better’ ways of doing this?

Actually what I would do in your position would be to create rules
(since your tasks depend on file extensions):

#this rules says that if a foo.transformed Filetask is called it depends
on foo.regular
rule “.transformed” => [".regular"] do |r|
#do the processing here to create the .transformed file

r gives you the actual FileTask triggering the rule and you can get

the path out of it
end

When you have your list of files do

deps=FileList["*.regular"].gsub(".regular",".transformed") #you can
obviously do all kinds of pathname magic here

and add it to a task

task :transform => deps do
#at this point you know that all transformed files are there and waiting
end

If it’s the output file you want to tie up then

file foo.output => deps

Cheers,
V.-

Put the transform task definition in front of your each loop.
You only create the task inside this loop.

task :transform do
end

my_files.each do |file|
file …
task :transform => file
end
next_file = ‘transformed_files.txt’
file next_file => :transform do

Do something with all transformed files to produce 1 output file

end

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