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Functions

Templates provide a number of functions that manipulate variables. Each variable data type has its own set of functions, which you can call using the dot (.) notation, for example:

<%= "lowercase".upper %>

LOWERCASE

Integer functions

Function Description
abs Get the absolute (non-negative) value.
to_string Convert an integer to a string.
to_s Alias for to_string.
to_float Convert integer to float.
to_f Alias for to_float.
times Create a list of integers, starting at 0 and ending with the integer.

Examples

Getting the absolute value of an integer:

<% if -5.abs == 5 %>
<h1>True<h1>
<% end %>

<h1>True</h1>

Converting an integer to a string:

<% if 25.to_s == "25" %>
<h1>True<h1>
<% end %>

<h1>True</h1>

Float functions

Function Description
abs Get the absolute (non-negative) value.
to_string Convert an integer to a string.
to_s Alias for to_string.
to_integer Convert float to integer, rounding it.
to_i Alias for to_integer.
round Round the float to the nearest whole value.
ceil Round the float to the upper whole value.
floor Round the float to the lower whole value.

Examples

Comparing a float and an integer:

<% if 25 == 25.4.to_i %>
<h1>True<h1>
<% end %>

<h1>True</h1>

String functions

Function Description
to_uppercase Convert string to uppercase lettering.
uppper Alias for to_uppercase.
to_lowercase Convert string to lowercase lettering.
lower Alias for to_uppercase.
trim Remove leading and trailing spaces and new lines.
capitalize Capitalize the first letter of a string.

Examples

Trim a string with extra leading and trailing spaces:

<p><%= "  messy string  " %></p>

<p>messsy string</p>

List functions

Function Description
enumerate Convert the list to a list of element position and element tuples.
reverse Convert the list to a new list of elements positioned from end to beginning.
rev Alias for reverse.
len Get the list length.
empty true if empty, false otherwise

Examples

Enumerate a list:

<% for tuple in ["one", "two"].enumerate %>
<li><%= tuple.0 %> &dash; <%= tuple.1 %>
<% end %>

<li>0 - one <li>
<li>1 - two</li>

Hashes

Function Description
keys Create a list of hash keys.
values Create a list of hash values.
iter Create a list of tuples, mapping keys to values. Used for iteration over a hash.

Global functions

Global functions are functions that can be used without a value, anywhere in the template.

Function Description
rwf_head Inject HTML and JavaScript that makes Rwf "just work". Use in the <head> element of a template.
rwf_turbo_stream Inject code that will create a <turbo-stream-source> element pointing to the right endpoint.
render Render a partial template. <%% is an alias for this function. 
<html>
  <head>
    <%- rwf_head() %>
    <title>Home page</title>
  </head>

<html>
  <body>
    <%- rwf_turbo_stream("/turbo-stream-endpoint") %>

<html>
  <body>
    <%- render("templates/index.html") %>