## Table of Contents
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- [Conditions --- `if`](#if)
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- [Loops --- `foreach`](#foreach)
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<!--toc-->
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## <span id="if"></span>Conditions
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## Conditions
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### Syntax
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Begin or continue conditional statement:
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( 'if' | 'elif' ) [ 'not' ] [ 'empty' ] ( VARIABLE | 'rtl' )
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( 'if' | 'elif' ) '(' any-c++-expression ')'
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Else block:
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'else'
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Each if/else block should be ended with `end` statement. For example:
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<% if not empty username %>
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<h1>Hello <% username %></h1>
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<% else %>
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<h1>Hello Visitor</h1>
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<% end %>
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<% if ( content.n % 2==0 ) %>
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<% n %> is odd.
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<% elif ( content.n % 3 ==0) % >
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<% n %> can be divided by 3 without reminder.
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<% end %>
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### Description
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This is ordinary `if`/`else if` statement. You can specify following conditions:
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- By specifying variable you check whether it is true.
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- By specifying `empty` keyword you may check if specific STL container is empty by calling its member `empty()`.
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- You can negate the result using `not`
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- You can also check whether current locale referred to Right-To-Left language like Hebrew, Arabic or Persian by specifying `rtl` keyword.
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This condition actually checks in dictionary if string "LTR" is translated as "RTL".
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- You can specify arbitrary C++ conditional expression withing round brackets `()`. _Note_: Do not forget to refer to content variables using `content.` prefix.
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## <span id="foreach"></span>Foreach block
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## Foreach block
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### Sytnax
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Major loop:
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'foreach' ['widget'] NAME 'in' VARIABLE
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In case of empty collection:
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'empty'
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Specify central body:
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'item'
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'separator'
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For example:
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<% foreach student in students %>
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<ul>
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<% item %>
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<li><% student.id %>, <% student.name %></li>
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<% end %>
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</ul>
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<% empty %>
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<h2>No students</h2>
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<% end %>
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You can specify delimiter for elements between `separator` and `item` block:
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<% foreach student in students %>
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<% separator %>, <% item %><% student.name %><% end %>
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<% end %>
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Would generate a list like: "Ron, John, Moshe"
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### Description
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`foreach` loop creates a for loop that iterates any STL collection. The given name is a reference to
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the type returned by iterator. For example, if students is `std::list<student_t>` then `student` in above
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example is defined as `student_t &student`.
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_Note:_ Template system uses one of following method for automatic type detection:
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1. C++0x `auto`
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2. C++0x `decltype`
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3. GCC `typeof`
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4. Boost Typeof
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At least one of them should be supported by the compiler in order to provide correct template generation.
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`empty` statement is equivalent to "else" so:
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<% foreach a in b %>
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<ul>
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<% item %><% a %><% end %>
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</ul>
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<% empty %>
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nothing
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<% end %>
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Is generated into code like:
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if(!content.b.empty()) {
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cout<<"<ul>";
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for(auto a_it=content.b.begin();a_it!=content.b.end();++a_it) {
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auto &a=*a_it;
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cout<<a;
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}
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cout<<"</ul>";
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}else{
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cout<<"nothing";
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}
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You must provide `<% item %>...<% end %>` block for any `foreach` statement.
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If `separator` is used it should be added between `separator` and `item` blocks.
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### Custom form rendering
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CppCMS forms system provides several options for rendering form widgets, but sometimes custom rendering
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may be needed. In this case, `foreach widget` statement is provided. In this case, widget is a reference
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to `cppcms::widget` and the collection should be `cppcms::form` or `cppcms::widgetset`.
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For example, rendering with "new line" separator:
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<% foreach widget w in form.my_set %>
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<% separator %><br/><% item %>
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<% if not empty w.msg %><% w.msg %>:<% end %>
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<% form input w %>
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<% if not w.is_valid %>:<% form error w %><% end %>
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<% end %>
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<% end %>
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