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HTML page generator example

In this example the genesis library is used to create a generator for a HTML page that contains tables with cities for different countries.

Template files

Base template

The base template is the entry point for generating the page.

I looks like this:

<!DOCTYPE html>
table {
font-family: arial, sans-serif;
border-collapse: collapse;
width: 300px;
td, th {
border: 1px solid #E7C324;;
text-align: left;
padding: 3px;
height: 20px;
tr:nth-child(even) {
background-color: #252525;
color: #E7C324;
color: #E7C324;
<title>Population of big cities</title>
<h1>Population of big cities.</h1>
<p>List of countries:</p>
<p style="font-size:12px">*The capital is marked <b>bold</b> and <a style="color:#1E90FF">blue</a></p>
<h3> <b>$var(country_name)</b></h3>

This template for a HTML page contains a loop (starting at line 40, ending at line 44) for iterating over a list of countries. For each country the name will be generated using the '$var' command (line 41). Then a template that generates the table will be called using the '$template' command (line 42). The loop ends with the command '$pool'.

Table template file

The template file for a table looks like this:

<td>$if(is_capital)<b><p style="color:#1E90FF">$fi$var(city_name)$if(is_capital)</p></b>$fi</td>
<td>$if(is_capital)<b><p style="color:#1E90FF">$fi$var(city_population)$if(is_capital)</p></b>$fi</td>

Each city will be represented in one line. In the coloumns are placed the name and the population of the city. For each city, we check if the city is the capital city of the country by calling '$if' command (lines 8 and 9). If the city has the index of the capital city, then the line containing the capital city is made bold and blue. The end of condition command '$fi' is called at the end.


The output HTML file containing a table with the cities of a specific country looks like this.


Countries and cities are stored in the structs country and city respectively:

struct country
std::string name_;
std::vector<city> cities_;
std::size_t capital_index_;
struct city
std::string name_;
int population_;

The structs are used in a configuration struct., The data is added manually in this case, but it could be read from file a file, a database, ...

struct config
std::string template_path_;
std::string source_template_file_;
std::string output_file_;
std::vector<country> countries_;

genesis's callback interface implementation

genesis offers a recipe callback interface which has to be implemented containing the generator logic.

For example the function for getting the variable contents looks like this:

std::string recipe_callback_impl::get_variable_content( const std::string& _variable_name )
std::string result( "" );
if( _variable_name == CITY_NAME )
result = config_.countries_[country_index_].cities_[city_index_].name_;
else if( _variable_name == CITY_POPULATION )
result = sxe::to_string( config_.countries_[country_index_].cities_[city_index_].population_ );
else if( _variable_name == COUNTRY_NAME )
result = config_.countries_[country_index_].name_;
return( result );

For each (city, population and country) the value is taken from a specific list with a specific index.

In the 'before_loop' method the indexes are set to 0 and in the 'after_loop_iteration' method they get incremented:

void recipe_callback_impl::after_loop_iteration( const std::string& _loop_name )
if( _loop_name == LOOP_COUNTRIES )
else if( _loop_name == LOOP_CITIES )

Checking the condition of the loop is done by checking if the index value is less than the size of the vector containing the data:

if( _loop_name == LOOP_COUNTRIES )
result = country_index_ < config_.countries_.size();

Checking the '$if' condition is pretty much the same: indexes are compared.

if( _condition_name == CONDITION_IS_CAPITAL )
result = config_.countries_[country_index_].capital_index_ == city_index_;

Generating the HTML page

Generating the HTMLpage is simple now. The configuration and callback objects are created. The callback is then passed to the recipe. Next the 'generate' method is called on the recipe object. Finally the content of the stream with the generated code is written into the output file by calling the 'write_to_file' method.

examples::config configuration;
examples::recipe_callback_impl recipe_callback( configuration );
sx::genesis::recipe source_recipe( configuration.source_template_file_, cb, configuration.template_path_ );
source_recipe.write_to_file( configuration.output_file_ );

Source code

The source code can be found on GitHub.