Rubyの5つの活用例
Rubyで何ができるのだろうと思ったことはないだろうか。まあ、可能性は無限大でしょうが、多少なりとも知られている事例についてお話しできれば幸いです。
Read an article coming from our Ruby Expert and learn why you don’t need to always youse hash.
When we want to aggregate some stuff, very often we use #each_with_object
or extend the regular loop 使用して #with_object
. But in most cases Ruby開発者 are using a plain hash as the aggregator and maybe it’s fine, but in this article, I’d like to show you that it doesn’t always have to be a hash.
We assume that all the files are placed in one directory (people
).
Let’s say we have the following people/people.csv
file:
First Name,Last Name,Age
John,Doe,24
Jane,Dee,45
Josh,Bee,55
Andrea,Boya,34
Andrew,Moore,54
We want to find the total of rows and the average age – we could write the following script:
people/parser.rb
require 'csv'
aggregated = CSV.foreach('people.csv', headers: true)
.withobject({ total: 0, totalage: 0 }) do |row, agg|
agg[:total] += 1
agg[:totalage] += row['Age'].toi
end
total = aggregated[:total]
averageage = aggregated[:totalage].to_f / total
puts "Total: #{total}"
puts "Average age: #{average_age}"
And yes, it does the thing but reading such a コード is a doubtful pleasure. It feels like a too low level. We can improve it by providing a dedicated aggregator for the loop.
people/age_aggregator.rb
class AgeAggregator
attrreader :total, :totalage
def initialize
@total = 0
@total_age = 0
end
def increment!
@total += 1
end
def incrementage!(age)
@totalage += age
end
def averageage
totalage.to_f / total
end
end
And then our loop would look as below:
people/parser.rb
require 'csv'
requirerelative './ageaggregator.rb'
aggregated = CSV.foreach('people.csv', headers: true)
.withobject(AgeAggregator.new) do |row, agg|
agg.increment!
agg.incrementage!(row['Age'].to_i)
end
puts "Total: #{aggregated.total}"
puts "Average age: #{aggregated.average_age}"
I think it’s much clearer.
We’ve written more code, but our lower-level details are extracted to the separate class. Now the main script reads much better.
Of course, you can argue that the example is too simple to put so much effort into refactoring, but c’mon – it’s just an example ;). If you had to aggregate more data, such aggregator objects are really the way to rescue.
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