CODEWITHSUNDEEP
rubyfileio
Mar
Mar

Reputation: 125

ruby - passing open file object to function as parameter

Why does this not work in Ruby when reading and writing to files?

def write_to_file(a_file)
    a_file.puts("hello")
end

a_file = File.new("test.txt", "w")
write_to_file(a_file)

the alternative i have found is to pass the file name to each function that reads or writes from it, and open and close it in that function.

why can't i open the file and pass that open file object to a function? does the a_file variable I am assigning not create a file object?

Upvotes: 0

Views: 291

Answers (1)

max
max

Reputation: 101891

File.new does create a file but its opened in buffered mode (or non-sync mode), unless filename is a tty. If you want to open a file and write contents to it the idiomatic way is:

File.open("test.txt", "w") do |file|
  file.write("hello")
end

This ensures that the file is closed when you're finished. That file handler can be passed around however you want:

def write_to_file(file)
  file.write("hello")
end

File.open("test.txt", "w") do |file|
  write_to_file(file)
end

Upvotes: 2

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