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<h1>group()<br>
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[<a class="el" href="group__adaptors.html">Adaptors</a>, <a class="el" href="group__lambdas.html">Lambdas</a>]</small>
</h1><a class="el" href="namespacesigc.html#a44">sigc::group()</a> alters an arbitrary functor by rebuilding its arguments from one or more lambda expressions.
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For each parameter that should be passed to the wrapped functor one lambda expression has to be passed into <a class="el" href="namespacesigc.html#a44">group()</a>. Lambda selectors can be used as placeholders for the arguments passed into the new functor. Arguments that don't have a placeholder in one of the lambda expressions are dropped.<p>
<dl compact><dt><b>Examples:</b></dt><dd><div class="fragment"><pre class="fragment"> <span class="keywordtype">void</span> foo(<span class="keywordtype">int</span>, <span class="keywordtype">int</span>);
<span class="keywordtype">int</span> bar(<span class="keywordtype">int</span>);
<span class="comment">// argument binding ...</span>
<a class="code" href="namespacesigc.html#a44">sigc::group</a>(&foo,10,sigc::_1)(20); <span class="comment">//fixes the first argument and calls foo(10,20)</span>
<a class="code" href="namespacesigc.html#a44">sigc::group</a>(&foo,sigc::_1,30)(40); <span class="comment">//fixes the second argument and calls foo(40,30)</span>
<span class="comment">// argument reordering ...</span>
<a class="code" href="namespacesigc.html#a44">sigc::group</a>(&foo,sigc::_2,sigc::_1)(1,2); <span class="comment">//calls foo(2,1)</span>
<span class="comment">// argument hiding ...</span>
<a class="code" href="namespacesigc.html#a44">sigc::group</a>(&foo,sigc::_1,sigc::_2)(1,2,3); <span class="comment">//calls foo(1,2)</span>
<span class="comment">// functor composition ...</span>
<a class="code" href="namespacesigc.html#a44">sigc::group</a>(&foo,sigc::_1,sigc::group(&bar,sigc::_2))(1,2); <span class="comment">//calls foo(1,bar(2))</span>
<span class="comment">// algebraic expressions ...</span>
<a class="code" href="namespacesigc.html#a44">sigc::group</a>(&foo,sigc::_1*sigc::_2,sigc::_1/sigc::_2)(6,3); <span class="comment">//calls foo(6*3,6/3)</span>
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The functor <a class="el" href="namespacesigc.html#a44">sigc::group()</a> returns can be passed into <a class="el" href="classsigc_1_1signal7.html#a0">sigc::signal::connect()</a> directly.<p>
<dl compact><dt><b>Example:</b></dt><dd><div class="fragment"><pre class="fragment"> <a class="code" href="classsigc_1_1signal.html">sigc::signal<void,int,int></a> some_signal;
<span class="keywordtype">void</span> foo(<span class="keywordtype">int</span>);
some_signal.<a class="code" href="classsigc_1_1signal7.html#a0">connect</a>(sigc::group(&foo,sigc::_2));
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Like in <a class="el" href="group__bind.html#ga8">sigc::bind()</a> you can bind references to functors by passing the objects through the <a class="el" href="namespacesigc.html#a317">sigc::ref()</a> helper function.<p>
<dl compact><dt><b>Example:</b></dt><dd><div class="fragment"><pre class="fragment"> <span class="keywordtype">int</span> some_int;
<a class="code" href="classsigc_1_1signal.html">sigc::signal<void></a> some_signal;
<span class="keywordtype">void</span> foo(<span class="keywordtype">int</span>&);
some_signal.<a class="code" href="classsigc_1_1signal7.html#a0">connect</a>(sigc::group(&foo,sigc::ref(some_int)));
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If you bind an object of a <a class="el" href="structsigc_1_1trackable.html">sigc::trackable</a> derived type to a functor by reference, a slot assigned to the group adaptor is cleared automatically when the object goes out of scope.<p>
<dl compact><dt><b>Example:</b></dt><dd><div class="fragment"><pre class="fragment"> <span class="keyword">struct </span>bar : <span class="keyword">public</span> sigc::trackable {} some_bar;
<a class="code" href="classsigc_1_1signal.html">sigc::signal<void></a> some_signal;
<span class="keywordtype">void</span> foo(bar&);
some_signal.<a class="code" href="classsigc_1_1signal7.html#a0">connect</a>(sigc::group(&foo,sigc::ref(some_bar)));
<span class="comment">// disconnected automatically if some_bar goes out of scope</span>
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