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| 54 | <H3><A NAME="SECTION0015632000000000000000"></A><A NAME="dom-accessor-methods"></A> |
| 55 | <BR> |
| 56 | 13.6.3.2 Accessor Methods |
| 57 | </H3> |
| 58 | |
| 59 | <P> |
| 60 | The mapping from OMG IDL to Python defines accessor functions for IDL |
| 61 | <tt class="keyword">attribute</tt> declarations in much the way the Java mapping |
| 62 | does. Mapping the IDL declarations |
| 63 | |
| 64 | <P> |
| 65 | <div class="verbatim"><pre> |
| 66 | readonly attribute string someValue; |
| 67 | attribute string anotherValue; |
| 68 | </pre></div> |
| 69 | |
| 70 | <P> |
| 71 | yields three accessor functions: a ``get'' method for |
| 72 | <tt class="member">someValue</tt> (<tt class="method">_get_someValue()</tt>), and ``get'' and |
| 73 | ``set'' methods for |
| 74 | <tt class="member">anotherValue</tt> (<tt class="method">_get_anotherValue()</tt> and |
| 75 | <tt class="method">_set_anotherValue()</tt>). The mapping, in particular, does not |
| 76 | require that the IDL attributes are accessible as normal Python |
| 77 | attributes: <code><var>object</var>.someValue</code> is <em>not</em> required to |
| 78 | work, and may raise an <tt class="exception">AttributeError</tt>. |
| 79 | |
| 80 | <P> |
| 81 | The Python DOM API, however, <em>does</em> require that normal attribute |
| 82 | access work. This means that the typical surrogates generated by |
| 83 | Python IDL compilers are not likely to work, and wrapper objects may |
| 84 | be needed on the client if the DOM objects are accessed via CORBA. |
| 85 | While this does require some additional consideration for CORBA DOM |
| 86 | clients, the implementers with experience using DOM over CORBA from |
| 87 | Python do not consider this a problem. Attributes that are declared |
| 88 | <tt class="keyword">readonly</tt> may not restrict write access in all DOM |
| 89 | implementations. |
| 90 | |
| 91 | <P> |
| 92 | In the Python DOM API, accessor functions are not required. If provided, |
| 93 | they should take the form defined by the Python IDL mapping, but |
| 94 | these methods are considered unnecessary since the attributes are |
| 95 | accessible directly from Python. ``Set'' accessors should never be |
| 96 | provided for <tt class="keyword">readonly</tt> attributes. |
| 97 | |
| 98 | <P> |
| 99 | The IDL definitions do not fully embody the requirements of the W3C DOM |
| 100 | API, such as the notion of certain objects, such as the return value of |
| 101 | <tt class="method">getElementsByTagName()</tt>, being ``live''. The Python DOM API |
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