Write to tempfile

rubyonrails-talk
1

Any ideas why the following succeeds in creating a temp file but does not write to it?

def format_q_gen       file = Tempfile.new([self.generator_file_name, ".rb"], "./lib/generators")       file.write("Hello") end

2

What makes you think it's not writing to it?

3

Hassan Schroeder wrote in post #1074521:

4

Interesting programming style :slight_smile:

Personally, I'd close the file so it gets written to disk, and then look at it. FWIW.

5

Hassan Schroeder wrote in post #1074525:

I am placing an undefined method after file.write("Hello"). Crashes the program and leaves the file so I can open it - its empty...

Interesting programming style :slight_smile:

Personally, I'd close the file so it gets written to disk, and then look at it. FWIW.

-- Hassan Schroeder ------------------------ hassan.schroeder@gmail.com Hassan Schroeder | about.me twitter: @hassan

Yes, I'm learning to program on my own... I don't believe anyone would pay for my work :slight_smile:

Thanks, you were right - it is writing to the file and I can see it after closing. Can I follow with one last question...

I have written a method, saved it in a table, and this is what I am writing to the temp file. Can I require the file and then call the method (getting the returned arguments) from the temp file as it is saved as a .rb file? eg...

def format_q_gen       file = Tempfile.new([generator_file_name, ".rb"], "./lib/generators")       file.write(question)       returned_question = generator_file_name # Calls the method in the tempfile       formatted = {         question: q["question_1"],         correct_answer_letter: "a"          }       file.close       file.unlink     end

6

I would personally write that method to be a little safer IMO. Yeah it’s true that you can sometimes guarantee that problems won’t happen but relying on that slim chance is bad, it’s better to let file closing operations fall onto an ensure so that if something does go wrong then you can at least guarantee you aren’t sloppy about it.

def demo_tempfile

file = Tempfile.new([“hello_world”, “.rb”], “./lib/generators”)

file.write(“$stdout.puts ‘hello world’”)

file.rewind

$stdout.puts file.read # Will output the source without evaling.

raise # Uncomment this line to see what I mean about ensure.

ensure

file.close!

end

7

Or even

Tempfile.open([“hello_world”, “.rb”], “./lib/generators”) do |file|

#do stuff with file

end

which closes the file for you at the end of the block.

Fred

8

Frederick Cheung wrote in post #1074604:

      file.rewind       $stdout.puts file.read # Will output the source without evaling.       # raise # Uncomment this line to see what I mean about ensure.     ensure       file.close!     end

Or even

Tempfile.open(["hello_world", ".rb"], "./lib/generators") do |file|   #do stuff with file end

which closes the file for you at the end of the block.

Fred

Thanks, trying to find out how to call a method contained in the file (method has same name as file)

Tempfile.open(["hello_world", ".rb"], "./lib/generators") do |file|

  # If the file is a method, how can I call the method here and get the returned

arguments?

9

The file can't "be" a method, but it may contain a string describing a method. You can read that string and invoke it using `eval`.

See: Module: Kernel (Ruby 1.9.3)

HTH,

10

Hassan Schroeder wrote in post #1074693: