DataReader

The DataReader gem is used to provide a standard mechanism for providing a YAML data source and loading data from it. DataReader is mainly used as a support gem that can be included by other libraries that need this functionality.

Installation

To get the latest stable release, add this line to your application's Gemfile:

gem 'data_reader'

To get the latest code:

gem 'data_reader', git: 'https://github.com/jeffnyman/data_reader'

After doing one of the above, execute the following command:

$ bundle

You can also install DataReader just as you would any other gem:

$ gem install data_reader

Usage

Including DataReader

You can include the DataReader in a class or module.

require "data_reader"

class Testing
  include DataReader
end

This will provide DataReader functionality on any instance of the class where DataReader is mixed in.

DataReader does not set defaults for anything. It provides a data_path variable that you can set. It also provides a data_source variable that will be populated with the result of a file that gets loaded from any specified data path.

Data Paths

Consider the following file and directory setup:

project_dir\
  config\
    config.yml

  data\
    stars.yml

  env\
    environments.yml

  test-data-reader.rb

All the code shown below would go in the test-data-reader.rb file.

With the above class in place and the above directory structure, you could do this:

test = Testing.new

puts test.data_path
puts test.data_source

This would print nothing for either of those values, showing that they have no default values as just stated. You could now do this:

test.data_path = 'data'

puts test.data_path

Here you are setting the data_path to a directory called data. The puts statement after that simply confirms that this was set. That will now set the data path for DataReader. Here the "data path" indicates where DataReader will look for data files. Thus you could load any file that is in that directory:

test.load 'stars.yml'

Loading causes the data from the file to be put into the data source. This can be referenced directly by the data_source attribute.

puts test.data_source

The puts call for the data_source will show you the contents of the YAML.

You could set the data source on the class instance if you wanted to:

class Testing
  include DataReader

  def data
    @data_source
  end
end

Now you can access the data via:

puts test.data

The reason this might be useful is because the data source may change but this way you refer to it via one variable.

Data Path on Class

You could have specified the data_path as a method of the class instead, like this:

class Testing
  include DataReader

  def data_path
    'data'
  end
end

Then you don't have to set the path specifically on the instance. That being said, you generally don't want to have both in place. Meaning either have the data_path defined on the test class or on the instance, not both. To show why this is problematic, consider this:

class Testing
  include DataReader

  def data_path
    'data'
  end
end

test = Testing.new

test.data_path = 'combined'

test.load 'stars.yml'

Here I'm setting the data_path twice. This works because the data file stars.yml is in the data. But now try this:

test.load 'config.yml'

That will fail. And that's because even though config.yml is in the combined directory, it's not in data. And that's what's being used here.

The upshot is that if you define a data_path on the class, that's what will be used.

Default Data Path

You may want to make sure that a default data path is always available should a data path not have been specifically set. You can do that as follows:

class Testing
  include DataReader

  def default_data_path
    'data'
  end
end

Keep in mind that DataReader will always favor whatever it has stored in data_path. The default_data_path can be used for a fallback. So, with the default data path specifed as above, consider this:

test = Testing.new

test.load 'stars.yml'
puts test.data_source

test.data_path = 'config'
configs = test.load 'config.yml'
puts test.data_source

Here the first load call works by using the default path. Then a data path is set and a file loaded from that path. Once that data path has been set, the default data path is no longer going to be used. If you want to be able to revert to the default, you need to set the data_path to nil. For example, here's the same code as the preceding with a few additions at the end:

test = Testing.new

test.load 'stars.yml'
puts test.data_source

test.data_path = 'config'
configs = test.load 'config.yml'
puts test.data_source

test.data_path = nil

test.load 'stars.yml'
puts test.data_source

The second call to load the stars.yml file reverts to using the default data path.

Just to show how this can fail, consider the following:

class Testing
  include DataReader

  def default_data_path
    'data'
  end
end

test = Testing.new

test.data_path = 'config'

test.load 'stars.yml'

This would fail to load stars.yml. While stars.yml is in data, which is the default, you have set a specific data path here to config.

The upshot is that a specific data path overrides the default.

Note that named sections will currently cause a failure. So for example:

users: &users
  admin:
  - username: admin
    password: admin

This would fail to load based on the &users part.

Multiple Data Files

You can load multiple YAML files. The load method takes a list of comma separated names of files that are in that same directory. So if you were to place all the above example YAML files in one directory, you could do this:

load 'config.yml, environments.yml, stars.yml'

When loading in multiple files, the data_source will hold the contents of all the files in the list.

Multiple Data Sources

You don't have to use the data_source value. For example, you could do this:

configs = app.load 'config.yml'
envs = app.load 'environments.yml'

In this case, the appropriate data would be stored in each variable. Do note that data_source will always contain the last data read by the load method. So in the above case, data_source would contain the contents of environments.yml even if you never intended to use that variable.

Setting a Data Pata

You can, at any time, set a data path. When you do, any calls to load will use that data path. Consider this example:

app.data_path = 'config'
configs = app.load 'config.yml'

app.data_path = 'env'
envs = app.load 'environments.yml'

Do note that if you had defined a data_path method in your class, as shown above, that will always overridde a local instance setting as shown in the preceding code.

Parameterizing Data

You can set environment variables in YAML files. To do this you have to use ERB, like this:

<%= ENV['XYZZY'] %>

To handle this, DataReader parses any values with ERB before it parses the YAML itself. Here's an example YAML file:

config:
  current:
    server: test
    user: jeff_nyman
    browser: <%= ENV['BROWSER'] %>

Now let's say I loaded up this file and looked at the data source:

app.load 'config.yml'
puts app.data_source

Assuming the BROWSER environment variable was set, the data_source variable would look as follows:

{
    "config" => {
        "current" => {
             "server" => "test",
               "user" => "jeff_nyman",
            "browser" => "chrome"
        }
    }
}

Method Calls on Data

The support for ERB allows for custom method calls. One that is included with DataReader is include_data, which can be used like this:

<%= include_data("config.yml") %>

Say that this line was included in line was in the YAML environment.yml from the above structure and you did this:

app.data_path = 'env'
app.load 'environments.yml'

This will load up environments.yml and, because of the include_data call would attempt to load the file config.yml. Note, however, that DataReader will attempt to load this from the same location as environments.yml. You can absolute or relative paths as part of the call, as such:

<%= include_data("../config/config.yml") %>

In this case, the value of data_source would contain both data sets, first the data from config.yml and then the data from environments.yml.

Extending DataReader

You can also extend, rather than include, DataReader. This means you deal with the class rather than an instance of it. For example:

require "data_reader"

class Testing
  extend DataReader
end

Testing.data_path = 'config'

puts Testing.data_path

Testing.load 'config.yml'

puts Testing.data_source

Note that you can provide methods as you did in the include case, but make sure they are defined on self. For example:

class Testing
  extend DataReader

  def self.data_path
    'config'
  end
end

If you were using default_data_path, likewise just make sure you prepend self to it.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec:all to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

The default rake command will run all tests as well as a RuboCop analysis.

To install this gem onto your local machine, run bundle exec rake install.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/jeffnyman/data_reader. The testing ecosystem of Ruby is very large and this project is intended to be a welcoming arena for collaboration on yet another testing tool. As such, contributors are very much welcome but are expected to adhere to the Contributor Covenant code of conduct.

To contribute to DataReader:

1. Fork the project.
2. Create your feature branch. (git checkout -b my-new-feature)
3. Commit your changes. (git commit -am 'new feature')
4. Push the branch. (git push origin my-new-feature)
5. Create a new pull request.

Author

• Jeff Nyman

Credits

This code is based upon the YmlReader gem. I wanted to give myself room to make a more generic version that may not be focused only on YAML files. More importantly, I wanted to clean up the implementation and documentation a bit.

License

DataReader is distributed under the MIT license. See the LICENSE file for details.