All about living assigns

This is a major release. The biggest change is completely redesigned engine for Drab.Live with nodrab option. Also introducting shared commanders, updates in Drab.Browser, performance and bug fixes.

Migration from 0.5

After installation, please remove all remaining priv/hashes_expressions.drab.cache.* files (they were renamed to drab.live.cache) and do a mix clean to recompile templates:

mix clean

Changes

Drab.Live

The main change in the new template engine is that now it is not injecting <span> everywhere. Now, it parses the html and tries to find the sourrounding tag and mark it with the attribute called drab-ampere. The attribute value is a hash of the previous buffer and the expression, so it is considered unique.

Consider the template, with initial value of 1 (given in render function in the Controller, as usual):

<p>Chapter <%= @chapter_no %>.</p>

which renders to:

<p drab-ampere="someid">Chapter 1.</p>

This drab-ampere attribute is injected automatically by Drab.Live.EExEngine. Updating the @chapter_no assign in the Drab Commander, by using poke/2:

chapter = peek(socket, :chapter_no)     # get the current value of `@chapter_no`
poke(socket, chapter_no: chapter + 1)   # push the new value to the browser

will change the innerHTML of the <p drab-ampere="someid"> to "Chapter 2." by executing the following JS on the browser:

document.querySelector('[drab-ampere=someid]').innerHTML = "Chapter 2."

This is possible because during the compile phase, Drab stores the drab-ampere and the corresponding pattern in the cache DETS file (located in priv/drab.live.cache).

Sometimes it must add a <span>

In case, when Drab can't find the parent tag, it injects <span> in the generated html. For example, template
like:

Chapter <%= @chapter_no %>.

renders to:

Chapter <span drab-ampere="someid">1</span>.

Avoiding using Drab (nodrab option)

If there is no need to use Drab with some expression, you may mark it with nodrab/1 function. Such expressions will be treated as a "normal" Phoenix expressions and will not be updatable by poke/2.

<p>Chapter <%= nodrab(@chapter_no) %>.</p>

In the future (Elixir 1.6 I suppose), the nodrab keyword will be replaced by a special EEx mark / (expression
will look like <%/ @chapter_no %>).

The @conn case

The @conn assign is often used in Phoenix templates. Drab considers it read-only, you can not update it
with poke/2. And, because it is often quite hudge, may significantly increase the number of data sent to
the browser. This is why Drab treats all expressions with only one assign, which happen to be @conn, as
a nodrab assign.

Shared Commanders

By default Drab runs the event handler in the commander module corresponding to the controller, which rendered the current page. Now it is possible to choose the module by simply provide the full path to the commander:

<button drab-click='MyAppWeb.MyCommander.button_clicked'>clickme</button>

Notice that the module must be a commander module, ie. it must be marked with use Drab.Commander, and the function must be whitelisted with Drab.Commander.public/1 macro.

Changes in Drab.Browser

All function in Drab.Browser were renamed to their bang version. This is because in the future release functions with and without bang will be more consist with Elixir standards - nobang function will return tuples, bangs will raise on error.

Warning: functions redirect_to!/2 and console!/2 are changed

In preparation to change all the functions in the module, this functions behavior have changed. Now, they are just bang version of the "normal" function, and they are not broadcasting anymore.

You should use broadcast_redirect_to!/2 and broadcast_console!/2 instead.