HashSelector

Select values from deeply nested/complex hashes with ease.

Consider a complex and deeply nested hash such as the following:

config =
{ databases: [
    { name: "myapp_production",
      user: "myapp",
      host: "db1"
    },
    { name: "legacy_db",
      host: "db2"
    }
  ],
  "redis": { host: "redis_server" }
}

Say we want to find the user name of legacy db but if we do not find it use a default value. With just the basic hash behavior this can be rather onerous. With HashSelector is it a breeze.

selector = HashSelector.new[:databases].find{|db| db[:name] == "myapp_production"}[:user]
selector.find_in(config) # => "myapp"

The selector definition line should be read as "a new selector that chooses the :databases item, finds an entry in it whose name is myapp_production, and selects its :user"

If the location specified by a HashSelector does not exist the hash it will raise a KeyError unless a block is provided. If a block is provided the block will be evaluated and its return value will returned from #find_in.

selector = HashSelector.new[:databases].find{|db| db[:name] == "myapp_test"}[:user]
selector.find_in(config) { "myapp" } # => "myapp"

In this example, there find fails because there is not entry in :databases with a name of myapp_test so the default (myapp) is returned instead.

HashSelectors are immutable and may be reused any any number of different hashes.

Add this line to your application's Gemfile:

gem 'hash-selector'

And then execute:

$ bundle

Or install it yourself as:

$ gem install hash-selector

1. Fork it ( https://github.com/pezra/hash-selector/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request