Allow rendering strings

[joeldrapper]

No description provided.

[bradgessler]

I pulled this gem into https://github.com/rubymonolith/demo/tree/render-strings

I still get these errors:

ArgumentError ('#<Method: BlogsController::Index#title() /Users/bradgessler/Projects/rubymonolith/demo/app/controllers/blogs_controller.rb:46>' is not an ActiveModel-compatible object. It must implement :to_partial_path.):

app/views/layouts/application_layout.rb:16:in `block (3 levels) in template'
app/views/layouts/application_layout.rb:16:in `block (2 levels) in template'
app/views/layouts/application_layout.rb:14:in `block in template'
app/views/layouts/application_layout.rb:13:in `template'
app/views/layouts/page_layout.rb:8:in `template'
app/views/application_view.rb:25:in `render'
app/views/application_view.rb:29:in `around_template'

Here's the code where I'm passing the block into the component as an argument: https://github.com//rubymonolith/demo/blob/07808942f21171cec51938b78c5011f34dd3c211/app/views/application_view.rb#L29-L31

These are the two places I'm trying to render it:

https://github.com//rubymonolith/demo/blob/07808942f21171cec51938b78c5011f34dd3c211/app/views/layouts/page_layout.rb#L12-L13

https://github.com//rubymonolith/demo/blob/07808942f21171cec51938b78c5011f34dd3c211/app/views/layouts/application_layout.rb#L16

Ideally if I pass a block into a class, I'd like to render it like this:

          hgroup do
            h1(&@title)
            h2(&@subtitle)
          end

Instead of like this:

          hgroup do
            h1 { render @title }
            h2 { render @subtitle }
          end

[joeldrapper]

When you render like this h1(&@title), @title must respond to to_proc, returning either a Proc accepting any number of arguments, or a Lambda that accepts exactly one argument.

I experimented with adding an arity check to the generated element methods so you could pass a Lambda that accepts no arguments, but doing this check for every element significantly slowed the overall performance.

If you use render and pass your @title without the &, after this PR, it will work if @title is:

1. an instance of Phlex::SGML or an instance of a subclass of Phlex::SGML;
2. a subclass of Phlex::SGML;
3. a Proc;
4. a Lambda accepting 0 or 1 arguments;
5. a Method accepting 0 or 1 arguments;
6. a String; or
7. an Enumerable of any of the above.

If an argument is accepted by the Proc/Lambda/Method, it will be called with the component instance.

Since render is used less than elements, the arity check isn't too expensive.

What's nice about this solution is it's compatible with many different things. You can accept a title argument, and the caller can give you any of these types, including a simple String.

[bradgessler]

I experimented with adding an arity check to the generated element methods so you could pass a Lambda that accepts no arguments, but doing this check for every element significantly slowed the overall performance.

This makes sense, thanks!

I'm wondering if there's a way to make the error messages for these types of performance trade-offs more informative. For example, if I try this:

hgroup do
  h1(&@title)
  h2(&@subtitle)
end

I'd find this a more useful exception message:

Error rendering h1(&@title). Try rendering from within the block: `h1 { render @title }`.

In theory this wouldn't impact performance, even if it takes a while to reflect on Ruby code to generate that message, because generating the exception stays out of the critical rendering path.