Extract part of string in Ruby

Question

So I'm given a text file containing:

Blade Runner (1982) [117 min] 
Full Metal Jacket (1987) [116 min] 
Monty Python and the Holy Grail (1975) [91 min] 
The Godfather (1972) [175 min]

and have to turn it into this:

Movie name: Blade Runner  
Movie release year: 1982 
Movie length (in mins): 117 

Movie name: Full Metal Jacket  
Movie release year: 1987 
Movie length (in mins): 116 

Movie name: Monty Python and the Holy Grail  
Movie release year: 1975 
Movie length (in mins): 91 

Movie name: The Godfather  
Movie release year: 1972 
Movie length (in mins): 175

First I iterate on each line, then I thought I should iterate on each part of the string, but that's where I get stuck, how do I do that? Do I use regex? How do I save a specific string that matches a regex?

Here's the current shell of the code, it stores the three parts into variables which are used to initialize a movie class who's to_s method prints in the desired format.

I know it's not right in many ways, but that's why I'm asking for help. variable = /regex/ is the line where the variable is assigned the thing captured by the regex and when /regex/ is for when that regex is matched.

class Movie
    def initialize (name, year, length) # constructor
        @name = name
        @year = year
        @length = length
    end

    def to_s    # returns string representation of object
        return "Movie Name: " + @name
            + "\nMovie release year: "
            + @year + "\nMovie Length (in min): "
            + @length + "\n"
    end
end

$movies = []
File.open("movies.txt").each do |line|
  if matches = /(.*)? \((\d+).*?(\d+)/.match(line)
    $movies << Movie.new(matches[1], matches[2], matches[3])
  end
end


for $movie in $movies do #what u got here is not index but the element in the array
    print $movie.to_s
end

Edit:

Fixed version of code, but print loop at end doesn't work.

Edit2: and nownit does. Thanks PeterPeiGuo!

@赢郭88888888: Can you explain your edit? Seems a bit much to go and destroy two-thirds of a question's content, and to top it off not even write a proper edit summary. — BoltClock
– BoltClock, Commented Feb 28, 2012 at 14:56

勿绮语 · Accepted Answer · 2012-04-22 23:10:32Z

3

m = /(.*)? \((\d+).*?(\d+)/.match("Blade Runner (1982) [117 min]")

edited Apr 22, 2012 at 23:10

answered Dec 2, 2011 at 2:59

勿绮语

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6 Comments

Portaljacker Over a year ago

Then what? That wasn't all I was asking about.

Portaljacker Over a year ago

You edited it to make my comment dumb. :P But thank you. Why does m become an array with exactly those elements? (yes I would like there to be no whitespace before or after the strings stored, handled with the regex, not chomp/trim)

Portaljacker Over a year ago

Awesome. So the regex looks for the whole expression basically, but only stored the things that match the inside of the curved brackets?

Portaljacker Over a year ago

Problem. :( For some reason the loop at the end fails for printing the objects. I get: "Cannot convert Movie into Integer"

勿绮语 Over a year ago

I modified last couple of lines and commented on the change

|

rabusmar · Accepted Answer · 2011-12-02 03:04:16Z

2

You can do something like this:

$movies = []
File.open("movies.txt").each do |line|
  if matches = /^(.*)\((\d+)\) \[(\d+)\smin\]/.match(line)
    $movies << Movie.new(matches[1], matches[2], matches[3])
  end
end

answered Dec 2, 2011 at 3:04

rabusmar

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1 Comment

Portaljacker Over a year ago

What? Ok, I did tag this as homework, I'm gonna need some explaining please. :P I'm ok on regex from JavaScript, but what are you doing here?

bkempner · Accepted Answer · 2011-12-02 03:14:05Z

# create string containing list of movies (numerous ways to load this data)
movie = <<-MOV
Blade Runner (1982) [117 min] 
Full Metal Jacket (1987) [116 min] 
Monty Python and the Holy Grail (1975) [91 min] 
The Godfather (1972) [175 min]
<<-MOV

# split movies into lines, then iterate over each line and do some regex
# to extract relavent data (name, year, runtime)
data = movies.split("\n").map do |s| 
  s.scan(/([\w\s]+)\ \((\d+)\)\ \[(\d+)\ min\]/).flatten }
end
# => [['Blade Runner', '1982', '117'], ... ]

# iterate over data, output in desired format.
data.each do |data| 
  puts "Movie name: #{data[0]}\nMovie release year: #{data[1]}\nMovie length: (in mins): #{data[2]}\n\n" }
end
# outputs in format you specified

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