Re: someVar to SOME_VAR

Saturday, February 14, 2009, 10:32:20 PM, Alex7 wrote:
>
> Sure, i wrap it, but razer to macro then function:
>
> <#macro ConvertToConstantName variable><#compress>
> ${variable?replace('(\\p{Upper})', '_$1', 'r')?upper_case}
> </#compress></#macro>
>
>
> Actually i don't know other difference between macro and function beside
> that function must have return statement.

That's a quite confusing aspect of FM indeed... But let me copy-paste
from the Manual:

  Methods and functions
  ---------------------

  A value that is a method or a function is used to calculate another
  value, influenced by the parameters you give to it.

  [...]

  What is the difference between a method and a function? As far as
  the template author is concerned, nothing. Well not really nothing,
  as methods typically come from the data-model (as they reflect the
  methods of Java objects), and functions are defined in templates
  (with the "function" directive -- an advanced topic), but both can
  be used on the same way.


  User-defined directives
  -----------------------

  A value of this type can be used as user-defined directive (with
  other words, as FreeMarker tag). An user-defined directive is a
  subroutine, something like a little reusable template fragment.

  [...]


  Function/method versus user-defined directive   <--- READ THIS!
  ---------------------------------------------

  [...] It's a frequent dilemma if you should use a function/method or
  an user-defined directive to implement something. The rule of thumb
  is: Implement the facility as user-defined directive instead of as
  function/method if:

  * ... the output (the return value) is markup (HTML, XML, etc.). The
    main reason is that the result of functions are subject to
    automatic XML-escaping (due to the nature of ${...}), while the
    output of user-defined directives are not (due to the nature of
    <@...>; its output is assumed to be markup, and hence already
    escaped).

  * ... it's the side-effect that is important and not the return
    value. For example, a directive whose purpose is to add an entry
    to the server log is like that. (In fact you can't have a return
    value for a user-defined directive, but some kind of feedback is
    still possible by setting non-local variables.)

  * ... it will do flow control (like for example list or if
    directives do). You just can't do that with a function/method
    anyway.

The Java methods of FreeMarker-unaware Java objects are normally
visible as methods in templates, regardless of the nature of the Java
method. That said, you have no choice there.

> Neither macro no function could be used inside tag AFAIK.

Functions can be used at the same places in the template as methods
can. So for example, you can write <@yourMethod yourFunction() />, but
not <@yourMethod <@yourOtherMethod /> />.

-- 
Best regards,
 Daniel Dekany


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