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| <title>OT/J Language Definition v1.3</title> |
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| <td class="back"><a id="top"></a><a href="s4.6.html" rel="prev"><< §4.6 Overriding access restrictions</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"><a href="s4.8.html" rel="next">§4.8 Callin precedence >></a></td> |
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| <div class="breadcrumb"><a class="nav" href="s4.html" rel="section">§4 Callin Binding</a></div> |
| <div class="sect depth2" id="s4.7"> |
| <h2 class="sect">§4.7 Callin binding with static methods<a class="img" href="s4.7.html" |
| title="PermaLink to §4.7 Callin binding with static methods"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h2> |
| <p>The normal case of callin bindings refers to non-static methods on both |
| sides (base and role). Furthermore, in Java inner classes can not define |
| static methods. Both restrictions are relaxed by the following rules: |
| |
| </p> |
| <div class="subsect depth3" id="s4.7.a"> |
| <h4 class="subsect">(a) <span class="title">Static role methods</span><a class="img" href="s4.7.a.html" |
| title="PermaLink to (a) Static role methods"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>A role class may define static methods (see also <a href="s1.2.1.f.html" title="§1.2.1.(f) Static role methods" |
| class="sect">§1.2.1.(f)</a>). |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s4.7.b"> |
| <h4 class="subsect">(b) <span class="title">Binding static to static</span><a class="img" href="s4.7.b.html" |
| title="PermaLink to (b) Binding static to static"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>A callin binding may bind a static role method to one or more |
| static base methods. It is, however, an error to bind a static base method to a non-static role method, |
| because such binding would require to lift a base object that is not provided. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s4.7.c"> |
| <h4 class="subsect">(c) <span class="title">before/after</span><a class="img" href="s4.7.c.html" title="PermaLink to (c) before/after"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>In addition to the above, <code>before</code> and <code>after</code> |
| callin bindings may also bind a static role method to non-static base methods. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s4.7.d"> |
| <h4 class="subsect">(d) <span class="title">replace</span><a class="img" href="s4.7.d.html" title="PermaLink to (d) replace"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>In contrast to <a href="#s4.7.c" title="§4.7.(c) before/after" class="sect">§4.7.(c)</a> above, a <code>replace</code> callin binding |
| cannot bind a static role method to a non-static base method. |
| |
| </p> |
| </div> |
| <p>The following table summarizes the combinations defined above: |
| |
| </p> |
| <table border="2" class="sep" cellpadding="5" width="80%"> |
| <tr class="z1"> |
| <td colspan="2" rowspan="2" align="right"><strong><-</strong> |
| </td> |
| <td colspan="2" align="center" rowspan="1"><strong>base method</strong></td> |
| </tr> |
| <tr class="z1"> |
| <td align="center" rowspan="1" colspan="1">static</td> |
| <td align="center" rowspan="1" colspan="1">non-static</td> |
| </tr> |
| <tr class="z2"> |
| <td rowspan="2" align="center" class="z1" colspan="1"><strong>role<br />method</strong></td> |
| <td align="center" class="z1" rowspan="1" colspan="1">static</td> |
| <td rowspan="1" colspan="1"><span class="green">OK</span></td> |
| <td rowspan="1" colspan="1"><code>before/after</code>: <span class="green">OK</span><br /><code>replace</code>: <span class="error">illegal</span></td> |
| </tr> |
| <tr class="z2"> |
| <td align="center" class="z1" rowspan="1" colspan="1">non-static</td> |
| <td rowspan="1" colspan="1"><span class="error">illegal</span></td> |
| <td rowspan="1" colspan="1"><span class="green">OK</span></td> |
| </tr> |
| </table> |
| <div class="subsect depth3" id="s4.7.e"> |
| <h4 class="subsect">(e) <span class="title">No overriding</span><a class="img" href="s4.7.e.html" title="PermaLink to (e) No overriding"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>Since static methods are not dynamically bound, <i>overriding</i> does not |
| apply in the normal semantics. Regarding callin bindings this has the |
| following consequences (assuming a role <code>RMid</code> played by |
| <code>BMid</code> plus its super-class <code>BSuper</code> and its sub-class |
| <code>BSub</code>. |
| |
| </p> |
| <ol> |
| <li>If a static base method <code>BMid.m</code> is bound by a callin binding |
| this has no effect on any method <code>m</code> in <code>BSub</code>. |
| </li> |
| <li>If a callin binding mentions a method <code>m</code> which is not present |
| in <code>BMid</code> but resolves to a static method in <code>BSuper</code> |
| the binding only affects invocations as <code>BMid.m()</code> but not |
| <code>BSuper.m()</code>. If the latter call should be affected, too, |
| the callin binding must appear in a role class bound to <code>BSuper</code>, |
| not <code>BMid</code>. |
| </li> |
| <li>In order to bind two static base methods with equal signatures, one being |
| defined in a sub-class of the other one, two roles have to be defined |
| where one role refines the <code>playedBy</code> clause of the other role |
| (say: <code>public class RSub extends RMid playedBy BSub</code>). |
| Now each role may bind to the static base method accessible in its direct |
| base-class. |
| </li> |
| </ol> |
| </div> |
| </div> |
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| <td class="back"><a href="s4.6.html" rel="prev"><< §4.6 Overriding access restrictions</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"><a href="s4.8.html" rel="next">§4.8 Callin precedence >></a></td> |
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| <div class="breadcrumb"><a class="nav" href="s4.html" rel="section">§4 Callin Binding</a></div> |
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