plugins/org.eclipse.objectteams.otdt.ui.help/guide/otjld/xdef/s2.4.1.html - objectteams/org.eclipse.objectteams - Gitiles

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          <div class="sect depth3" id="s2.4.1">
             <h3 class="sect">&sect;2.4.1&nbsp;Role creation via a lifting constructor<a class="img" href="s2.4.1.html"
                   title="PermaLink to &sect;2.4.1&nbsp;Role creation via a lifting constructor"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png"
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             <p>Lifting uses the default constructor for roles (see <a href="s2.3.1.html" title="&sect;2.3.1&nbsp;Implicit role creation"
                   class="sect">&sect;2.3.1</a>).
                This constructor can be invoked from client code, if the following rules are respected.

             </p>
             <div class="subsect depth4" id="s2.4.1.a">
                <h4 class="subsect">(a)&nbsp;<span class="title">Team context</span><a class="img" href="s2.4.1.a.html" title="PermaLink to (a)&nbsp;Team context"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png"
                           alt="" /></a></h4>
                <p>The lifting constructor can be used only within the enclosing team of
                   		the role to be instantiated. Thus, qualified allocation expressions
                   		(<code>someTeam.new SomeRole(..)</code>) may never use the lifting constructor.

                </p>
             </div>
             <div class="subsect depth4" id="s2.4.1.b">
                <h4 class="subsect">(b)&nbsp;<span class="title">Fresh base object</span><a class="img" href="s2.4.1.b.html"
                      title="PermaLink to (b)&nbsp;Fresh base object"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png"
                           alt="" /></a></h4>
                <p>If the argument to a lifting constructor invocation is a <code>new</code>
                   		expression, creating a fresh base object, the use of the lifting constructor
                   		is safe. Otherwise the rules of (c) below apply.

                </p>
             </div>
             <div class="subsect depth4" id="s2.4.1.c">
                <h4 class="subsect">(c)&nbsp;<span class="title">Duplicate role runtime check</span><a class="img" href="s2.4.1.c.html"
                      title="PermaLink to (c)&nbsp;Duplicate role runtime check"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png"
                           alt="" /></a></h4>
                <p>If it cannot be syntactically derived, that the argument to a lifting
                   		constructor is a freshly created base object (b), a compile time warning will
                   		signal that an additional runtime check is needed: It must be prevented that
                   		a new role is created for a base object, which already has a role of the
                   		required type in the given team. It is not possible to replace an existing
                   		role by use of the lifting constructor. At runtime, any attempt to do so
                   		will cause a <code>org.objectteams.DuplicateRoleException</code> to be thrown.
                   		This exception can only occur in situations where the mentioned compile
                   		time warning had been issued.
                   		<br /><a href="s6.1.html" title="&sect;6.1&nbsp;Reflection" class="sect">&sect;6.1</a> will introduce reflective functions
                   which can be used to manually prevent errors like a duplicate role.

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          <div class="breadcrumb"><a class="nav" href="s2.html" rel="section">&sect;2&nbsp;Role Binding</a>&nbsp;&gt;&nbsp;<a class="nav" href="s2.4.html" rel="section">&sect;2.4&nbsp;Explicit role creation</a></div>
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                  width="88" /></a><address>&copy; Stephan Herrmann, Christine Hundt, Marco Mosconi</address>
          			OT/J version 1.3 &mdash; last modified: 2010-05-18
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	<td class="next"><a href="s2.4.2.html" rel="next">§2.4.2 Role creation via a regular constructor >></a></td>
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	<div class="breadcrumb"><a class="nav" href="s2.html" rel="section">§2 Role Binding</a> > <a class="nav" href="s2.4.html" rel="section">§2.4 Explicit role creation</a></div>
	<div class="sect depth3" id="s2.4.1">
	<h3 class="sect">§2.4.1 Role creation via a lifting constructor<a class="img" href="s2.4.1.html"
	title="PermaLink to §2.4.1 Role creation via a lifting constructor"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png"
	alt="" /></a></h3>
	<p>Lifting uses the default constructor for roles (see <a href="s2.3.1.html" title="§2.3.1 Implicit role creation"
	class="sect">§2.3.1</a>).
	This constructor can be invoked from client code, if the following rules are respected.

	</p>
	<div class="subsect depth4" id="s2.4.1.a">
	<h4 class="subsect">(a) <span class="title">Team context</span><a class="img" href="s2.4.1.a.html" title="PermaLink to (a) Team context"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png"
	alt="" /></a></h4>
	<p>The lifting constructor can be used only within the enclosing team of
	the role to be instantiated. Thus, qualified allocation expressions
	(<code>someTeam.new SomeRole(..)</code>) may never use the lifting constructor.

	</p>
	</div>
	<div class="subsect depth4" id="s2.4.1.b">
	<h4 class="subsect">(b) <span class="title">Fresh base object</span><a class="img" href="s2.4.1.b.html"
	title="PermaLink to (b) Fresh base object"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png"
	alt="" /></a></h4>
	<p>If the argument to a lifting constructor invocation is a <code>new</code>
	expression, creating a fresh base object, the use of the lifting constructor
	is safe. Otherwise the rules of (c) below apply.

	</p>
	</div>
	<div class="subsect depth4" id="s2.4.1.c">
	<h4 class="subsect">(c) <span class="title">Duplicate role runtime check</span><a class="img" href="s2.4.1.c.html"
	title="PermaLink to (c) Duplicate role runtime check"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png"
	alt="" /></a></h4>
	<p>If it cannot be syntactically derived, that the argument to a lifting
	constructor is a freshly created base object (b), a compile time warning will
	signal that an additional runtime check is needed: It must be prevented that
	a new role is created for a base object, which already has a role of the
	required type in the given team. It is not possible to replace an existing
	role by use of the lifting constructor. At runtime, any attempt to do so
	will cause a <code>org.objectteams.DuplicateRoleException</code> to be thrown.
	This exception can only occur in situations where the mentioned compile
	time warning had been issued.
	<br /><a href="s6.1.html" title="§6.1 Reflection" class="sect">§6.1</a> will introduce reflective functions
	which can be used to manually prevent errors like a duplicate role.

	</p>
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	<div class="breadcrumb"><a class="nav" href="s2.html" rel="section">§2 Role Binding</a> > <a class="nav" href="s2.4.html" rel="section">§2.4 Explicit role creation</a></div>
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	OT/J version 1.3 — last modified: 2010-05-18
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