views

Everything that is remotely connected to views in a Rails application.

Table of Contents

• Forms

  • Form Basics

• Partials

  • Default values for partial locals

Forms

Form basics

Generating basic forms be done with the form_tag, however, this will lead to a lot of manual work that rails can handle. Should you be in a situation where you cannot use the form builder and need to build a form by hand, railsgiudes has you covered. The following will handle the creation of forms with the form builder.

Often times when working on a rails application and dealing with forms, chances are you want to modify or create a resoucrce (in the 'new' and 'edit' view for example). To make that easier, we can make use of the form builder, by using form_for to generate our form. Let's assume we have an Article model that has fields for a title and content. We can than pass an instance of that model to form_for, which will yield a form builder object (passed to the block as f in the example below) which will handle a lot of work for us.

= form_for @article, url: {action: "create"} do |f|
  = f.text_field :title
  = f.text_field :content
  = f.submit "Create"

If we had defined artilces as a resouce in our routes, we could even use

= form_for @article do |f|
  = f.text_field :title
  = f.text_field :content
  = f.submit "Create"

and rails will figure out if we are generating a new record or modifying an exiting.

Partials

Default values for partial locals

First things first: I feel like setting default values for locals in partials should not be happening in any production application. I think this kind of logic does not belong into the view, especially not in a partial.

Nonetheless, there are situations where it is needed more convenient to set the value of a local inside the partial. This happened for example in a heavily mocked prototype that was just used for internal demoing pruposes to me lately. Thinking about it now, I feel like I could probably have found a better solution for this as well, without too much effort. But nonetheless, should I ever again need to do this, I'll write it down here.

The approach is rather simple: Every local passed to a partial can be accessed via the local_assigns hash. So basically all we have to do is to check if the key we want to set a default value is present and set the default value if it's not the case. There are multiple approaches to this, but I liked the following the most for its reability (even though it's kind of long):

- default_value = "default_value" if local_assigns[:default_value].nil?

Further reading

• There are a lot of different approaches in this Stack Overflow Question