How can I use a local (or per view) variable in Sinatra with Haml partials?

Question

I have a Haml partial in Sinatra to handle all of my 'page open' items like meta tags.

I would love to have a variable for page_title in this partial and then set that variable per view.

Something like this in the partial:

%title @page_title

Then in the view, be allowed to do something like:

@page_title = "This is the page title, BOOM!"

I have read a lot of questions/posts, etc. but I don't know how to ask for the solution to what I am trying to do. I'm coming from Rails where our devs usually used content_for but they set all that up. I'm really trying to learn how this works. It seems like I have to define it and use :locals in some way but I haven't figured it out. Thank you in advance for any tips!

Answer 1

You pass variables into Sinatra haml partials like this:

page.haml

!!!
%html{:lang => 'eng'}
    %body
        = haml :'_header', :locals => {:title => "BOOM!"}

_header.haml

   %head
       %meta{:charset => 'utf-8'}
       %title= locals[:title]

In the case of a page title I just do something like this in my layout btw:

layout.haml

%title= @title || 'hardcoded title default'

Then set the value of @title in routes (with a helper to keep it short).

But if your header is a partial then you can combine the two examples like:

layout.haml

!!!
%html{:lang => 'eng'}
    %body
        = haml :'_header', :locals => {:title => @title}

_header.haml

   %head
       %meta{:charset => 'utf-8'}
       %title= locals[:title]

app.rb

helpers do
  def title(str = nil)
    # helper for formatting your title string
    if str
      str + ' | Site'
    else
      'Site'
    end
  end
end


get '/somepage/:thing' do
  # declare it in a route
  @title = title(params[:thing])
end