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## cppcms::base\_content
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This is a simple polymorphic class from which every cppcms content template should be derided. It allows dynamic casting of the content for the target application:
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class base_content {
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public:
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virtual ~base_content() {};
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};
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## cppcms::base\_view
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### Members
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- **`worker_thread &worker`** -- reference to the worker thread that called the rendering procedure.
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- **`ostream &cout`** -- reference to the output stream that output is rendered to.
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### How Derived Classes are created:
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This is the class that every view generated from the template system is derived from.
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Every derived class defines the important public member --- `content` --- the reference to the user defined content class.
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It also creates member functions for each implemented template. For example:
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<% c++ #include "data.h" %>
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<% namespace my_view %>
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<% class message uses data::message %>
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<% template render() %>
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<html>
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<body>
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<h1><% message %> World!</h1>
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</body>
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<html>
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<% end template %>
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<% end class %>
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<% end namespace %>
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The above template is rendered to C++ output:
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#include "data.h"
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namespace my_view {
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struct message :public cppcms::base_view
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{
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data::message &content;
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cppcms::transtext::trans const *tr;
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message(cppcms::base_view::settings _s,data::message &_content):
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cppcms::base_view(_s),content(_content)
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{
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tr=_s.worker->domain_gettext("my_view");
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};
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virtual void render() {
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cout<<"\n"
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"<html>\n"
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" <body>\n"
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" <h1>";
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cout<<escape(content.message);
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cout<<" World!</h1>\n"
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" </body>\n"
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"<html>\n"
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"";
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} // end of template render
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}; // end of class message
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} // end of namespace my_view
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### Member functions
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#### Default filter
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template<typename T>
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string escape(T const &v)
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This is the default filter. It performs the rendering of the input parameter to text. This function is always called when the template parameter is substituted without filters, i.e.:
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<% param %>
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is converted to
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cout<<escape(content.param);
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By default, it uses `ostream` to render the output, however it provides several specializations:
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- **`string escape(string const &s)`** -- performs HTML escaping of string.
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- **`string escape(std::tm const &v)`** -- converts `std::tm` time to human readable format.
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#### Provided Filters
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They are called when some filters are given. Each filter has the following possible signatures:
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string filter_name(Type const &inp);
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string filter_name(Type const &inp,string param);
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Where `inp` is a given filter input and `param` is the filter parameter.
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- **`string raw(string s)`** -- raw filter, does nothing. It is used to push some html data without escaping. For example:
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<% some_html_page | raw %>
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- **`string intf(int val,string f)`** -- format integer number. It uses `boost::format` for this purpose. For example:
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Decimal <% num %> is hexadecimal <% num | intf("%x"); %>
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- **`string strftime(std::tm const &t,string f)`** -- formats the output string using std::strftime call. For example:
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<% date | strftime("%d/%m/%Y") %>
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It has tho following "shortcuts" for showing the date only, the time or the time with seconds:
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string date(std::tm const &t);
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string time(std::tm const &t);
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string timesec(std::tm const &t);
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- **`string urlencode(string const &s);`** -- encode string for URL. For example:
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<a href="http://site/article/<% link | urlencode %>">
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#### Other member functions
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boost::format format(string const &f);
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Function that returns i\a `boost::format` object constructed with `f` and with disabled exceptions. In generally `boost::format` throws an exception in case of an incorrect format or parameters list --- this is not such a good behavior for displaying various data.
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It is used mostly by gettext and ngettext implementations. For example
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<% ngt "We have one apple","We have %1% apples",n using n %>
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Is rendered to:
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cout<<format(tr->gettext("We have one apple","We have %1% apples",n)) % escape(n);
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Thus it would not throw an exception in case of "one apple".
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