Crystalmeta helps you control meta tags through I18n and/or manually. It plays well with OpenGraph and Twitter Cards.

It gives you 3 helpers:

1. meta(options) — available in both controller & views.

Accepts Hash.

Collects meta tags for future use:

# folded hashes
meta og: {title: "The Rock (1996)", type: "video.movie"}

# one level hash
meta "og:title" => "The Rock (1996)", "og:type" => "video.movie"
meta :"og:image" => "the-rock.png"

2. meta_tag(name) — available in views

Accepts String or Symbol.

Returns value for a certain tag:

<title><%= meta_tag 'og:title' %></title>

3. meta_tags(pattern = //)

Returns all meta tags which names match the pattern. Under the hoods it uses the three-qual to pattern match (like in Enumerable#grep).

<%= meta_tags /^og:/ %>

displays in this case:

<meta property="og:url" content="http://www.imdb.com/title/tt0117500/" />
<meta property="og:image" content="/assets/the-rock.png" />
<meta property="og:title" content="The Rock (1996)" />
<meta property="og:type" content="video.movie" />

Please note that:

• image_path is automatically used for og:image or og:image:url (video_path for og:video and audio_path for og:audio respectively), so you don't have to bother setting explicit paths;
• og:url is set to controller.request.url.

I18n translations

Crystalmeta tries to fetch translations and merge them in this order (consider an example for pages#show action):

• meta._defaults — application defaults (lowest-priority)
• meta.pages._defaults — controller defaults
• meta.pages.show — action

Tags set manually by the meta helper will be given the highest priority.

Namespaced controllers

Crystalmeta uses controller_path in order to get the translation scope, so if you have a namespaced controller, for instance Library::BooksController, then the show action will use: meta.library.books._defaults & meta.library.books.show respectively.

Aliases

Crystalmeta uses translations for the edit action for update:

• meta._defaults
• meta.movies._defaults
• meta.movies.edit
• meta.movies.update

And new for create:

• meta._defaults
• meta.movies._defaults
• meta.movies.new
• meta.movies.create

You can omit defining translations for update & create actions if they're the same.

Displaying only certain meta tags using a pattern

Usually I set window title with Crystalmeta separately (I call it head for example) and I don't want to display it in meta tags, so I can do:

<%= meta_tags /:/ %>

It will filter tag names using /:/ === name.

You may wish to use a Proc in some cases:

<%= meta_tags Proc.new{|name| name != "head"} %>

Interpolation

You can interpolate meta tags like this:

<% 
meta({
  "og:title"     => "The Rock (1996)",
  "og:site_name" => "IMDb",
  "head"         => "%{og:title} — %{og:site_name}"
}) 
%>

meta_tag :head will return "The Rock (1996) — IMDb".

Please use this feature with care to avoid SystemStackError.

Caveats

Merging tags

When tags are merged (while fetching translations or collecting with meta) Crystalmeta doesn't do anything smart — it just merges hashes brutally. So if you defined a tag like that:

en:
  meta:
    _defaults:
      og:
        title: IMDb

and then you redefine it in different style:

meta 'og:title' => 'The Rock (1996)'

then you'll just get 2 tags in the end:

<%= meta_tags /og:title/ %>

will display

<meta property="og:title" content="IMDb" />
<meta property="og:title" content="Newer IMDb" />

So you'd better prefer one style.

Date/Time

Crystalmeta will convert Date/Time/Datetime objects to iso8601 automatically, so if you don't want it, pass them as strings.

Arrays

To maximize OpenGraph compatibility, Crystalmeta handles Arrays in similar way:

<% meta :og => {:image => %w{1.png 2.png}} %>
<%= meta_tags /og:image/ %>

will display:

<meta property="og:image" content="/assets/1.png" />
<meta property="og:image" content="/assets/2.png" />

Multiple images with properties

If you have multiple images with properties like this:

<meta property="og:image:url" content="/assets/rock.jpg" />
<meta property="og:image:width" content="300" />
<meta property="og:image:height" content="300" />
<meta property="og:image:url" content="/assets/rock2.jpg" />
<meta property="og:image:url" content="/assets/rock3.jpg" />
<meta property="og:image:height" content="1000" />

then you'll have to set them in a special way:

<% meta 'og:image' => [
  {:url => 'rock.jpg', :width => 300, :height => 300},
  {:url => 'rock2.jpg'},
  {:url => 'rock3.jpg', :height => 1000},
] %>

or:

en:
  meta:
    pages:
      show:
        og:image:
          - url: rock.jpg
            width: 300
            height: 300
          - url: rock2.jpg
          - url: rock3.jpg
            height: 1000

It will sort keys so that the url property is on top.