Changes between Version 21 and Version 22 of MarkupTemplates

Timestamp:

Jul 12, 2006, 3:06:03 AM (18 years ago)

Author:

mgood

Comment:

document the two usage forms of py:choose

MarkupTemplates

@@ -13 +13 @@
 == Template Context ==
 
-Rendering a template boils down to applying one or more template files to some input data. This input data is represented as a [wiki:ApiDocs/MarkupTemplate#markup.template:Context Context] object in Markup. A context is basically a stack of dictionaries that manages the namespace scopes during processing: for example, some variable may be able under a given name inside a loop, but not outside of that loop.
+Rendering a template boils down to applying one or more template files to some input data. This input data is represented as a [wiki:ApiDocs/MarkupTemplate#markup.template:Context Context] object in Markup. A context is basically a stack of dictionaries that manages the namespace scopes during processing: for example, some variable may be available under a given name inside a loop, but not outside of that loop.
 
 Regardless of its stack behavior during templating processing, a context is usually initialized from a single dictionary:
@@ -108 +108 @@
 }}}
 
-The rationale behind the second form is that directives not always map naturally to elements in the template. In such cases, the [wiki:MarkupTemplates#pystrip py:strip] directive can be used to strip off the unwanted element, or the directive can simply be used as an element.
+The rationale behind the second form is that directives do not always map naturally to elements in the template. In such cases, the [wiki:MarkupTemplates#pystrip py:strip] directive can be used to strip off the unwanted element, or the directive can simply be used as an element.
 
 === `py:content` ===
@@ -171 +171 @@
 <ul>
   <li class="collapse">Bar</li>
+</ul>
+}}}
+
+Attributes with the value `None` are omitted, so given `foo={'class': None}` in the context for the same template this would produce:
+
+{{{
+#!xml
+<ul>
+  <li>Bar</li>
 </ul>
 }}}
@@ -233 +242 @@
 === `py:choose` / `py:when` / `py:otherwise` ===
 
-This set of directives provides advanced contional processing: one of several alternatives is rendered depending on which of the `py:when` directives evaluates to a truth value.
+This set of directives provides advanced contional processing for rendering one of several alternatives.  The first matching `py:when` directive will be rendered or, if no `py:when` directive matches, the `py:otherwise` directive will be rendered.
+
+If the `py:choose` directive is empty the nested `py:when` directives will be tested for truth:
 
 {{{
@@ -240 +251 @@
   <span py:when="0 == 1">0</span>
   <span py:when="1 == 1">1</span>
+  <span py:otherwise="">2</span>
+</div>
+}}}
+
+This would produce the following output:
+
+{{{
+#!xml
+<div>
+  <span>1</span>
+</div>
+}}}
+
+If the `py:choose` directive contains an expression the nested `py:when` directives will be tested for equality to the parent `py:choose` value:
+
+{{{
+#!xml
+<div xmlns:py="http://markup.edgewall.org/" py:choose="1">
+  <span py:when="0">0</span>
+  <span py:when="1">1</span>
   <span py:otherwise="">2</span>
 </div>