Calculate sum of objects for each unique object property in Ruby

Posted by macek on Stack Overflow See other posts from Stack Overflow or by macek
Published on 2010-04-12T21:57:48Z Indexed on 2010/04/12 22:03 UTC
Read the original article Hit count: 171

Filed under:

ruby

|

best-practices

|

arrays

|

hash

|

enumerable

I was helping with an answer in this question and it sparked a question of my own.

Pie is an object that has a pieces array made of of PiePiece objects.
Each PiePiece has a flavor attribute

How do I create a hash that looks like this:

# flavor => number of pieces
{
  :cherry => 3
  :apple => 1
  :strawberry => 2
}

This works, but I think it could be improved

def inventory
  hash = {}
  pieces.each do |p|
    hash[p.flavor] ||= 0
    hash[p.flavor] += 1
  end
  hash
end

Any ideas?

© Stack Overflow or respective owner

Related posts about ruby

Setting up Rails to work with sqlserver

as seen on Stack Overflow - Search for 'Stack Overflow'
Ok I followed the steps for setting up ruby and rails on my Vista machine and I am having a problem connecting to the database. Contents of database.yml development: adapter: sqlserver database: APPS_SETUP Host: WindowsVT06\SQLEXPRESS Username: se Password: paswd Run rake db:migrate… >>> More
marshal data too short!!!

as seen on Stack Overflow - Search for 'Stack Overflow'
My application requires to keep large data objects in session. There are like 3-4 data objects each created by parsing a csv containing 150 X 20 cells having strings of 3-4 characters. My application shows this error- "marshal data too short". I tried this- Deleting the old session table. Deleting… >>> More
Sinatra and XML POST request

as seen on Stack Overflow - Search for 'Stack Overflow'
I don't know is it my mistake or no. So i have that code: <code> post '/singin/get_token' do content_type :xml puts request.body.read puts xmlRequest xmlRequest = REXML::Document.new(request.body.read) ... </code> And when i post something like that: <code> <?xml… >>> More
how to change ruby path from /usr/bin/ruby to /usr/local/bin/ruby

as seen on Stack Overflow - Search for 'Stack Overflow'
reading around the various ruby install tutorials it's required to change path from /usr/bin/ruby to /usr/local/bin/ruby but i cant seem to be able to do it. Ultimately i want to install Ruby 1.9.2, should i uninstall 1.8.7 or what? i tried to install Ruby 1.9.2 with macports, the installation seemed… >>> More
strange bundler error: tar_input.rb:49:in `initialize': not in gzip format (Zlib::GzipFile::Error) o

as seen on Stack Overflow - Search for 'Stack Overflow'
i am getting a strange bundler error when running bundle pack with bundler 0.9.12 any ideas? (see pastie for a better formatted code: http://pastie.org/881328 ) /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/package/tar_input.rb:49:in `initialize': not in gzip format (Zlib::GzipFile::Error) … >>> More

Related posts about best-practices

Batch Best Practices and Technical Best Practices Updated

as seen on Oracle Blogs - Search for 'Oracle Blogs'
The Batch Best Practices for Oracle Utilities Application Framework based products (Doc Id: 836362.1) and Technical Best Practices for Oracle Utilities Application Framework Based Products (Doc Id: 560367.1) have been updated with updated and new advice for the various versions of the Oracle… >>> More
Partial template specialization of free functions - best practices

as seen on Stack Overflow - Search for 'Stack Overflow'
As most C++ programmers should know, partial template specialization of free functions is disallowed. For example, the following is illegal C++: template <class T, int N> T mul(const T& x) { return x * N; } template <class T> T mul<T, 0>(const T& x) { return T(0); } //… >>> More
Object Oriented PHP Best Practices

as seen on Stack Overflow - Search for 'Stack Overflow'
Say I have a class which represents a person, a variable within that class would be $name. Previously, In my scripts I would create an instance of the object then set the name by just using: $object->name = "x"; However, I was told this was not best practice? That I should have a function set_name()… >>> More
Good place to look for example Database Designs - Best practices

as seen on Stack Overflow - Search for 'Stack Overflow'
I have been given the task to design a database to store a lot of information for our company. Because the task is rather big and contains multiple modules where users should be able to do stuff, I'm worried about designing a good data model for this. I just don't want to end up with a badly designed… >>> More
Notification Email Best Practices--From Server Setup to Programming

as seen on Stack Overflow - Search for 'Stack Overflow'
All, I'm in the process now of building a SaaS tool that allows network admins to generate notification emails to the members of the end-users of our platform (among many many other things). I'm running into a bit of an "out of my expertise" wall, as I know there are a lot of variables involved… >>> More