私有方法“ puts”需要“ string”：String（NoMethodError）

Question

I am using ruby: 1.9.3

File named as restaurant.txt which has the data like this:

|"Aloo Fry"| "Carbohydrates bahut hai" | "Nahi Khana"
|"Moong"| "protein bahut hai" | "Khana Hai"
|"Egg"|"Protein hai but non veg"| "Nahi khana hai"

Now what I have to do is to take the last string and remove the existing line. output file have to be the same file and should look like:

 Nahi Khana Khana Hai Nahi Khana hai 

if ARGV.length != 1
  puts "Input only the one file at a time"
  exit
end
foodie = ARGV[0]
puts "you have entered file: #{foodie}"
puts "Hold your horses... we are processing"
File.open(foodie, "r+").each do |line|
  new_line = line.split("|")[-1]
  puts new_line
  line.puts new_line
end

I am getting the error:

private method `puts' called for "Nahi Khana":String (NoMethodError)

Answer 1

@Whooper has identified the problem with your code. I have therefore chosen to suggest another approach to constructing the desired file.

Let's first construct a file that contains the string given in your example.

FName = 'temp'
str =<<END
|"Aloo Fry"| "Carbohydrates bahut hai" | "Nahi Khana"
|"Moong"| "protein bahut hai" | "Khana Hai"
|"Egg"|"Protein hai but non veg"| "Nahi khana hai"
END

File.write(FName, str)
  #=> 149 (characters)

Confirm its contents:

puts File.read(FName)
|"Aloo Fry"| "Carbohydrates bahut hai" | "Nahi Khana"
|"Moong"| "protein bahut hai" | "Khana Hai"
|"Egg"|"Protein hai but non veg"| "Nahi khana hai"

You can read the file and use String#scan with a simple regular expression and Array#join to construct the string you wish to keep.

s = File.read(FName).scan(/\"[^|]+$/).join("\n")
  #=> "\"Nahi Khana\"\n\"Khana Hai\"\n\"Nahi khana hai\"\n" 
puts s
"Nahi Khana"
"Khana Hai"
"Nahi khana hai"

The regular expression reads, "match a double quote followed by all characters other than a pipe ( "|" ) to the end of the line". Each match will begin with the first double-quote following the last pipe in the line.

Lastly, write s back to the same file, overwriting its contents.

File.write(FName, s)
  #=> 42

Have a look.

puts File.read(FName)
"Nahi Khana"
"Khana Hai"
"Nahi khana hai"

The use of IO::read is sometimes referred to as gulping a file (as a string). ¹ That's fine as long as the file is not too large. If it's a very large file it may be necessary to read the file line-by-line, modify the line and then write that to a temporary file. When the temporary file is complete the original file can be deleted and, if desired, the temporary file can be renamed to the name of the original file. You could do that as follows.

TMP_FName = 'tmp'

f = File.open(TMP_FName, 'w')
File.foreach(FName) do |line|
  f.puts line.scan(/\"[^|]+$/).join("\n")
end
f.close
File.delete(FName)
File.rename(TMP_FName, FName)

Confirm:

puts File.read(FName)
"Nahi Khana"
"Khana Hai"
"Nahi khana hai"

^{1 I don't know if there is a comparable term for the use of IO#write ; perhaps disgorging a string into a file . Though read and write are IO (class) methods, they are commonly involked on the class File . That's OK because File.superclass #=> IO , so File inherits those methods from IO .}

Answer 2

This statement line.puts new_line causes the error.

I am assuming that what you want to achieve here is to write new_line to your output file and maybe you thought that line is a File object, which is not, because line is a string which contains each line read from your input file. Besides, your File.open method is only read-only state so you cannot write on that file.

So I suggest that you store first each new_line in a list then after you finished processing all lines from your input file, have another loop where you will overwrite your file to reflect the results you got.

if ARGV.length != 1
  puts "Input only the one file at a time"
  exit
end
foodie = ARGV[0]
puts "you have entered file: #{foodie}"
puts "Hold your horses... we are processing"

new_lines = []
File.open(foodie, "r+").each do |line|
  new_lines.push(line.split("|")[-1])
end

File.open(foodie, "w+") do |file|
  new_lines.each { |element| file.puts(element) }
end