Micro Moustache

Minimal moustache implementation for Arduino and other micro controllers.

Introduction

Moustache is a logic-less template processor. This makes it easy to replace text or in- or exclude parts of text. This is especially handy for creating dynamic HTML!

This library is a minimal implementation of the original library. The original library is available for many platforms but, to my knowledge, not Arduino... Until now!

The original project can be found at http://mustache.github.io/ and the manual at http://mustache.github.io/mustache.5.html. However, in this library only a few functionalities are implemented.

Passing variables to the template

Variables need to be present in an array of the structure moustache_variable_t. The original implementation of Moustache uses json but this is overkill for micro controllers. Micro Moustache uses an array of a structure that holds a key and a value.

typedef struct moustache_variable
{
    const char *key;
    String value;
} moustache_variable_t;

Some features like looping are not possible using this data structure but keeps it simple.

The value is defined as a string. This makes it easy to convert values to string as a lot of conversions are already implemented in the String class.

A typical definition of the variables will look like this. The immediate values below can of course be replaced by variables.

  moustache_variable_t substitutions[] = {
      {"Version", "1.0"},
      {"LoggedIn", String(false)},
      {"UserName", String("Jake")},
      ...
      ...
    };

Implemented features

The following sections contain a list of implemented features. The examples are take from the official Moustache documentation.

Replacing variables

Variables can be replaced using the syntax: {{variable}}.

example:

Hello {{name}}
You have just won {{value}} dollars!

with variables:

  moustache_variable_t substitutions[] = {
    {"name", "Chris"},
    {"value", String(10000)}
  };
  auto result = moustache_render(taxes, substitutions);
  Serial.println(result);

will render:

Hello Chris
You have just won 10000 dollars!

Include Section

Sections can be included using the syntax: {{#expr}}Text to be included{/expr}.

The expression needs to be a boolean expression and, as the String class is used, booleans convert to "0" or "1".

example:

{{#in_ca}}
Well, {{taxed_value}} dollars, after taxes.
{{/in_ca}}

with variables:

  moustache_variable_t substitutions[] = {
    {"taxed_value", String(10000 - (10000 * 0.4))},
    {"in_ca", String(true)}
  };
  auto result = moustache_render(taxes, substitutions);
  Serial.println(result);

will render:

Well, 6000.0 dollars, after taxes.

Inverted Section

Sections can be included using the syntax: {{^expr}}Text to be included{/expr}.

The expression needs to be a boolean expression and, as the String class is used, booleans convert to "0" or "1".

example:

{{#in_ca}}
Well, {{taxed_value}} dollars, after taxes.
{{/in_ca}}
{{^in_ca}}
And no taxes paid!
{{/in_ca}}

with variables:

  moustache_variable_t substitutions[] = {
    {"taxed_value", String(10000 - (10000 * 0.4))},
    {"in_ca", String(false)}
  };
  auto result = moustache_render(taxes, substitutions);
  Serial.println(result);

will render:

And no taxes paid!

Collaboration

Collaboration is appreciated and bug reports or feature requests are welcome!

Change history

• Oct 2022
  • Initial version
• Feb 2023
  • Changed the const String& value in the moustache variable to String value. This will allow to change the variable without recreating the complete array. This update requires removing the const for the moustache_variable_t.