## Conditions |
## Table of Contents |
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- [Conditions --- `if`](#if) |
- [Loops --- `foreach`](#foreach) |
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## <span id="if"></span>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' ) |
( '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 %> |
<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 %> |
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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. |
- By specifying `empty` keyword you may check if specific STL container is empty by calling its member `empty()`. |
- 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 `rtl` keyword. |
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 using `content.` prefix. |
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## Foreach block |
## <span id="foreach"></span>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' |
'separator' |
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For example: |
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<% foreach student in students %> |
<ul> |
<% item %> |
<li><% student.id %>, <% student.name %></li> |
<% end %> |
</ul> |
<% empty %> |
<h2>No students</h2> |
<% end %> |
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You can specify delimiter for elements between `separator` and `item` block: |
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<% foreach student in students %> |
<% separator %>, <% item %><% student.name %><% end %> |
<% 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 |
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`. |
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_Note:_ Template system uses one of following method for automatic type detection: |
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1. C++0x `auto` |
2. C++0x `decltype` |
3. GCC `typeof` |
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 %> |
<ul> |
<% item %><% a %><% end %> |
</ul> |
<% empty %> |
nothing |
<% end %> |
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Is generated into code like: |
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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"; |
} |
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You must provide `<% item %>...<% end %>` block for any `foreach` statement. |
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 |
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`. |
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For example, rendering with "new line" separator: |
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<% 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 %> |
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