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| <td class="back"><a id="top"></a><a href="s1.3.1.d.html" rel="prev"><< §1.3.1.(d) Lack of subtyping</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"><a href="s1.3.1.f.html" rel="next">§1.3.1.(f) tsuper >></a></td> |
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| <div class="breadcrumb"><a class="nav" href="s1.html" rel="section">§1 Teams and Roles</a> > <a class="nav" href="s1.3.html" rel="section">§1.3 Acquisition and implicit inheritance of role classes</a> > <a class="nav" href="s1.3.1.html" rel="section">§1.3.1 Acquisition and implicit inheritance of role classes</a></div> |
| <div class="subsect depth4" id="s1.3.1.e"> |
| <h4 class="subsect">§1.3.1.(e) <span class="title">Dynamic binding of types</span><a class="img" href="s1.3.1.e.html" |
| title="PermaLink to (e) Dynamic binding of types"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
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| <p>Overriding an acquired role by a new role class has the following |
| implication: If an expression or declaration, which is evaluated on behalf of |
| an instance of team <code>T</code> or one of its contained roles, |
| refers to a role <code>R</code>, <code>R</code> will always |
| resolve to <code>T.R</code> even if <code>R</code> was introduced in |
| a super-team of <code>T</code> and even if the specific line of code |
| was inherited from a super-team or one of its roles. |
| Only the dynamic type of the enclosing team-instance is used to determine |
| the correct role class (see below for an example). |
| |
| </p> |
| <p>A special case of dynamically binding role types relates to so-called class literals |
| (see <a href="http://java.sun.com/docs/books/jls/second_edition/html/expressions.doc.html#251530" |
| class="ext">JLS §15.8.2</a>). |
| Role class literals are covered in <a href="s6.1.c.html" title="§6.1.(c) Class literals for roles" |
| class="sect">§6.1.(c)</a>. |
| |
| </p> |
| <p>The above is strictly needed only for cases involving implicit inheritance. |
| It may, however, help intuition, to also consider the directly acquired |
| role <code>T.R</code> in (b) to override the given role <code>S.R</code>. |
| |
| </p> |
| <div class="codecomment"> |
| In line 17 of <a href="s1.html#l1.3.1-1" class="listing">Listing 1.3.1-1</a> the implicitly inherited method <code>n</code> is called |
| with the result of an invocation of <code>m</code>. Although |
| <code>n</code> was defined in <code>S</code> (thus with argument type |
| <code>S.R2, see line 6</code>) in the context of <code>T</code> it |
| expects an argument of <code>T.R2</code>. This is correctly provided by |
| the invocation of <code>m</code> in the context of <code>T</code>. |
| |
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| <td class="back"><a href="s1.3.1.d.html" rel="prev"><< §1.3.1.(d) Lack of subtyping</a></td> |
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| <td class="next"><a href="s1.3.1.f.html" rel="next">§1.3.1.(f) tsuper >></a></td> |
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| <div class="breadcrumb"><a class="nav" href="s1.html" rel="section">§1 Teams and Roles</a> > <a class="nav" href="s1.3.html" rel="section">§1.3 Acquisition and implicit inheritance of role classes</a> > <a class="nav" href="s1.3.1.html" rel="section">§1.3.1 Acquisition and implicit inheritance of role classes</a></div> |
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