[Checkins] SVN: z3c.form/trunk/ Add ``z3c.form.error.ComputedErrorViewMessage`` factory for easy creation of dynamically computed error messages.

[Dan Korostelev]

Log message for revision 103731:
  Add ``z3c.form.error.ComputedErrorViewMessage`` factory for easy creation of dynamically computed error messages.

Changed:
  U   z3c.form/trunk/CHANGES.txt
  U   z3c.form/trunk/src/z3c/form/error.py
  U   z3c.form/trunk/src/z3c/form/error.txt

-=-
Modified: z3c.form/trunk/CHANGES.txt
===================================================================
--- z3c.form/trunk/CHANGES.txt	2009-09-11 10:03:01 UTC (rev 103730)
+++ z3c.form/trunk/CHANGES.txt	2009-09-11 10:07:12 UTC (rev 103731)
@@ -5,6 +5,9 @@
 Version 2.2.0 (unreleased)
 --------------------------
 
+- Feature: Add ``z3c.form.error.ComputedErrorViewMessage`` factory for easy
+  creation of dynamically computed error messages.
+
 - Bug: Replace dots with hyphens when generating form id from its name.
 
 - Refactored OutputChecker to its own module to allow using 

Modified: z3c.form/trunk/src/z3c/form/error.py
===================================================================
--- z3c.form/trunk/src/z3c/form/error.py	2009-09-11 10:03:01 UTC (rev 103730)
+++ z3c.form/trunk/src/z3c/form/error.py	2009-09-11 10:07:12 UTC (rev 103731)
@@ -31,7 +31,11 @@
     discriminators = ('error', 'request', 'widget', 'field', 'form', 'content')
     )
 
+ComputedErrorViewMessage = value.ComputedValueCreator(
+    discriminators = ('error', 'request', 'widget', 'field', 'form', 'content')
+    )
 
+
 def ErrorViewDiscriminators(
     errorView,
     error=None, request=None, widget=None, field=None, form=None, content=None):

Modified: z3c.form/trunk/src/z3c/form/error.txt
===================================================================
--- z3c.form/trunk/src/z3c/form/error.txt	2009-09-11 10:03:01 UTC (rev 103730)
+++ z3c.form/trunk/src/z3c/form/error.txt	2009-09-11 10:07:12 UTC (rev 103731)
@@ -91,7 +91,37 @@
 
 Much better, isn't it?
 
+We can also provide dynamic error view messages that are computed each time we
+get an error. For example, we have an IAdult interface that have minimal age of
+18:
 
+  >>> class IAdult(zope.interface.Interface):
+  ...     age = zope.schema.Int(title=u'Age', min=18)
+
+Now, let's create a function that will be called by a message value adapter,
+it receives one argument, a special ``z3c.form.value.ComputedValue`` object
+that will have all needed attributes: error, request, widget, field, form and
+content. Let's use one of them:
+
+  >>> def getAgeTooSmallErrorMessage(value):
+  ...     return u'Given age is smaller than %d, you are not adult.' % (
+  ...         value.field.min)
+
+Now, register the computed view message:
+
+  >>> ComputedAgeMessage = error.ComputedErrorViewMessage(
+  ...     getAgeTooSmallErrorMessage, error=TooSmall, field=IAdult['age'])
+  >>> zope.component.provideAdapter(ComputedAgeMessage, name='message')
+
+Now, the error view snippet will show dynamically generated message:
+
+  >>> view = error.ErrorViewSnippet(
+  ...     TooSmall(), TestRequest(), None, IAdult['age'], None, None)
+  >>> view.update()
+  >>> print view.render()
+  <div class="error">Given age is smaller than 18, you are not adult.</div>
+
+
 Registering Custom Error Views
 ------------------------------