7 Patterns to Refactor JavaScript Applications: Policy Objects

Note: This is part six (prev/next) of a seven part series that starts here.

Business logic always includes some boolean rules for data models, such as if a User is activated, or if a Student is passing. These rules interpret model attributes and return true or false, describing whether the object does or does not pass the policy.

For example, if a process sends an email to a given set of users, a Policy Object can be used to filter that set down to only those users that are email-able. A User would pass the Policy Object if they: have an email address, that email address has been verified, and they have not unsubscribed from correspondence.

Brian Helmkamp describes the potential overlap in concept between a Policy Object and a Query Object or a Service Object. He writes, “Policy Objects are similar to Service Objects, but I use the term ‘Service Object’ for write operations and ‘Policy Object’ for reads. They are also similar to Query Objects, but Query Objects focus on executing SQL to return a result set, whereas Policy Objects operate on domain models already loaded into memory.”

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7 Patterns to Refactor JavaScript Applications: View Objects

Note: This is part five (prev/next) of a seven part series that starts here.

When a model has associated logic or attributes that are used exclusively for creating a representation of the model—as in HTML for a website or JSON for an API endpoint—a best practice is to avoid storing those values directly on the model.

Storing view-specific attributes on the model can create confusion about what is truth (stored in the database) and what is purely representational. View Objects, then, act as an adapter between the truth and the representation of the truth.

For example, the truth of an imagined inventory item is that the price attribute stored in the database is 599 cents. But the representation for the product page may be a mutation of the truth, such as $5.99.

It would be inappropriate to store the representational data as a secondary price attribute on the model. It would be even worse to inject the formatting logic into the template.

What View Objects do is dress up the data, by way of transforming, adding, or removing data properties, returning a new object for use in the presentation layer. This approach creates a nice home for our presentation-specific logic and attributes, keeping it removed from the model truth.

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A Look at Rails 5

From the start, Rails was praised for being the easiest way to get Ruby on the web. It was the easiest option, and the best. Since then, many other options have arrived, but Rails is still the industry leading framework for Ruby developers.

As is tradition, this April at RailsConf 2015 in Atlanta, the creator of Rails, David Heinemeier Hansson (aka DHH) took the stage to announce what was new in Rails and to mark the release of Rails 5. This fits with the schedule of a major release every two years. And of course, folks were excited to get in early and see what our BDFL had to say about the future of Rails.

Here’s a look at some of the highlights.

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Goodbye MVP, Hello v1

You've done it!

It all started with a simple concept and two friends in your garage. After weeks of coding and tweaking, you've proven that your business idea is the greatest thing since sliced bread. You used the Build, Measure, Learn cycle to find out what your customers want, and you're pretty sure you have a product market fit.

Now what?

It's time to build your v1. In this post, we'll look at how to take the most important lessons from the information you've gleaned during the MVP stage of your product's lifecycle and apply them to building the first full release of your product.

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7 Patterns to Refactor JavaScript Applications: Query Objects

Note: This is part four (prev/next) of a seven part series that starts here.

Database queries, even simple ones, can be both repetitive and hard to comprehend. With more complex queries, especially ones that embed data from multiple collections or tables, this process can become downright unintelligible.

Query objects provide a nice tool for extracting database query logic and associated operations into a contained module, pulling the logic out into a more maintainable and readable structure, while also providing a very readable API where the query object is used.

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