Rails .erb file

Rails use erb as its default engine to render views. It uses a specific implementation called erubi. To use erb in Rails, files should all have a. During the course of my investigation I found that there are three elements used:. This tag indicates that there will be an expression inside it. The main point: The application will render the result of executing the code inside this tag. The controller will ask the model to retrieve the first user from the database.

Then it will store it in an instance variable called user:. If we would like to display the first three user attributes in a view, we would use HTML and erb code like the following:. Remember: The app will render the result of executing code inside expression tags. The difference is that the application won't render the result of executing the code. They are frequent on ruby expressions.

Imagine you are building a view to display all the users in your database. This is the first time you have taken the full advantage of associations, which enable you to easily pull data from related objects. The format used is variable.

If click on any listed record then it will show you the following screen. Create a new file called edit. This code is very similar to the new method except action to be updated instead of creating and defining an id. Why because it will create interaction with the Model easily.

At this point, we need some modification in the list method's view file. It will give you the listing of all the books along with Edit option. Now, you edit this information and then click the Save Changes button. This will result in a call to update method available in the controller file and it will update all the changed attribute.

Notice that the update method does not need any view file because it's using either show or edit methods to show its results. Removing information from a database using Ruby on Rails is almost too easy. You do not need to write any view code for the delete method because this method is using list method to display the result. So, let's just modify list. The :confirm parameter presents a JavaScript confirmation box asking if you really want to perform the action.

If the user clicks OK, the action proceeds, and the item is deleted. ERB gets variables from a Binding , an object that provides access to the instance methods and variables that are owned by another object.

If you do not specify a Binding, the result method gets a Binding from the top-level object, which will probably own very little. Fortunately, every Ruby class has a private binding instance method to provide Bindings that points to itself, so we can easily extend any object to provide ERB with a Binding.

If the ERB object is enclosed in a method, and we want it to use the variables of the host object, we get a Binding for the host like this:. To enable ERB to use the variables from a separate object, we must first ensure that it has a public method to provide a Binding. We can then get a Binding at any later point:.

You may protect your application from ERB by running it in a new thread. If you specify an integer as a second parameter when you create the renderer, then the template will be processed in a new thread which has a safe level equal to the given integer:.

Safe level 4 provides maximum isolation. At this level, the specified binding must be marked as trusted for ERB to use it. If you need to set the third or fourth parameters, but do not want ERB to run in a new thread, use 0 as the second parameter.

The third parameter of new specifies optional modifiers, most of which alter when newline characters will be automatically added to the output. The erb utility processes a given template and sends the result to the standard output. This enables you to generate files directly from templates, by redirecting the output:. The template can automatically use built-in Ruby classes, such as String and File. To allow it to access standard or third-party libraries, use the -r option.

This option works in the same way as the require keyword.