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