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| <h1 align="center"><a href="../index.html">Boost.Python</a></h1> |
| |
| <h2 align="center">Headers <boost/python/init.hpp></h2> |
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| <hr> |
| |
| <h2>Contents</h2> |
| |
| <dl class="page-index"> |
| <dt><a href="#introduction">Introduction</a></dt> |
| |
| <dt><a href= |
| "#init-expressions"><em>init-expressions</em></a></dt> |
| |
| <dt><a href="#classes">Classes</a></dt> |
| |
| <dd> |
| <dl class="page-index"> |
| <dt><a href="#init-spec">Class template <code>init</code></a></dt> |
| |
| <dd> |
| <dl class="page-index"> |
| <dt><a href="#init-spec-synopsis">Class template |
| <code>init</code> synopsis</a></dt> |
| |
| <dt><a href="#init-spec-ctors">Class <code>init</code> |
| constructors</a></dt> |
| |
| </dl> |
| </dd> |
| |
| <dt><a href="#optional-spec">Class template |
| <code>optional</code></a></dt> |
| |
| <dd> |
| <dl class="page-index"> |
| <dt><a href="#optional-spec-synopsis">Class template |
| <code>optional</code> synopsis</a></dt> |
| </dl> |
| </dd> |
| </dl> |
| </dd> |
| |
| <dt><a href="#examples">Example(s)</a></dt> |
| </dl> |
| <hr> |
| |
| <h2><a name="introduction"></a>Introduction</h2> |
| |
| <p><code><boost/python/init.hpp></code> defines the interface for |
| exposing C++ constructors to Python as extension class |
| <code>__init__</code> functions.</p> |
| |
| <h2><a name="init-expressions"><em>init-expressions</em></a></h2> |
| An <em>init-expression</em> is used to describe a family of |
| <code>__init__</code> methods to be generated for an extension class, and |
| the result has the following properties: |
| |
| <blockquote> |
| <dl class="properties"> |
| <dt><b>docstring:</b> An <a href="definitions.html#ntbs">ntbs</a> |
| whose value will bound to the method's <code>__doc__</code> |
| attribute</dt> |
| |
| <dt><b>keywords:</b> A <a href= |
| "args.html#keyword-expression">keyword-expression</a> which will be |
| used to name (a trailing subsequence of) the arguments to the |
| generated <code>__init__</code> function(s).</dt> |
| |
| <dt><b>call policies:</b> An instance of a model of <a href= |
| "CallPolicies.html">CallPolicies</a>.</dt> |
| |
| <dt><b>argument types:</b> An MPL sequence of C++ argument types |
| which will be used to construct the wrapped C++ object. An init |
| expression has one or more |
| <b>valid prefixes</b> which are given by a sequence of |
| prefixes of its argument types.</dt> |
| </dl> |
| </blockquote> |
| |
| <h2><a name="classes"></a>Classes</h2> |
| |
| <h3><a name="init-spec"></a>Class template <code>init<T1 =</code> |
| <i>unspecified</i><code>, T2 =</code> |
| <i>unspecified</i><code>,</code>...<code>Tn</code> = |
| <i>unspecified</i><code>></code></h3> |
| |
| <p>A <a href="../../../mpl/doc/refmanual/forward-sequence.html">MPL sequence</a> which |
| can be used to specify a family of one or more <code>__init__</code> |
| functions. Only the last <code>T</code><i><small>i</small></i> supplied |
| may be an instantiation of <a href= |
| "#optional-spec"><code>optional</code></a><code><</code>...<code>></code>.</p> |
| |
| <h4><a name="init-spec-synopsis"></a>Class template <code>init</code> |
| synopsis</h4> |
| <pre> |
| namespace boost { namespace python |
| { |
| template <T1 = <i>unspecified</i>,...T<i>n</i> = <i>unspecified</i>> |
| struct init |
| { |
| init(char const* doc = 0); |
| template <class Keywords> init(Keywords const& kw, char const* doc = 0); |
| template <class Keywords> init(char const* doc, Keywords const& kw); |
| |
| template <class CallPolicies> |
| <em>unspecified</em> operator[](CallPolicies const& policies) const |
| }; |
| }} |
| </pre> |
| |
| <h4><a name="init-spec-ctors"></a>Class template <code>init</code> |
| constructors</h4> |
| <pre> |
| init(char const* doc = 0); |
| template <class Keywords> init(Keywords const& kw, char const* doc = 0); |
| template <class Keywords> init(char const* doc, Keywords const& kw); |
| </pre> |
| |
| <dl class="function-semantics"> |
| <dt><b>Requires:</b> If supplied, <code>doc</code> is an <a href= |
| "definitions.html#ntbs">ntbs</a>. If supplied, <code>kw</code> is the |
| result of a <a href="args.html#keyword-expression"></a></dt> |
| |
| <dt><b>Effects:</b> The result is an <em>init-expression</em> whose |
| <em>docstring</em> is <code>doc</code> and whose <em>keywords</em> are |
| a reference to <code>kw</code>. If the first form is used, the |
| resulting expression's <em>keywords</em> are empty. The expression's |
| <em>call policies</em> are an instance of <a href= |
| "default_call_policies.html#default_call_policies-spec">default_call_policies</a>. |
| If <code>T</code><i><small>n</small></i> is <a href= |
| "#optional-spec"><code>optional</code></a><code><U1, U2,</code>... |
| <code>U</code><small><i>m</i></small><code>></code>, the |
| expression's <em>valid prefixes</em> are given by:</dt> |
| |
| <dd> |
| <blockquote> |
| (<code>T1, T2,</code>...<code>T</code><i><small>n-1</small></i>), |
| (<code>T1, T2,</code>...<code>T</code><i><small>n-1</small></i> |
| <code>, U1</code>), |
| (<code>T1, T2,</code>...<code>T</code><i><small>n-1</small></i> |
| <code>, U1, U2</code>), |
| ...(<code>T1, T2,</code>...<code>T</code><i><small>n-1</small></i> |
| <code>, U1, U2,</code>...<code>U</code><i><small>m</small></i>). |
| </blockquote> |
| Otherwise, the expression has one <em>valid prefix</em> given by the |
| the template arguments the user specified. |
| </dd> |
| </dl> |
| |
| <h4><a name="init-spec-observers"></a>Class template <code>init</code> |
| observer functions</h4> |
| <pre> |
| template <class Policies> |
| <em>unspecified</em> operator[](Policies const& policies) const |
| </pre> |
| |
| <dl class="function-semantics"> |
| <dt><b>Requires:</b> Policies is a model of <a href= |
| "CallPolicies.html">CallPolicies</a>.</dt> |
| |
| <dt><b>Effects:</b> Returns a new <a href= |
| "#init-expressions"><em>init-expression</em></a> with all the same |
| properties as the <code>init</code> object except that its <em>call |
| policies</em> are replaced by a reference to |
| <code>policies</code>.</dt> |
| </dl> |
| |
| <h3><a name="optional-spec"></a>Class template <code>optional<T1 |
| =</code> <i>unspecified</i><code>, T2 =</code> |
| <i>unspecified</i><code>,</code>...<code>Tn</code> = |
| <i>unspecified</i><code>></code></h3> |
| |
| <p>A <a href="../../../mpl/doc/refmanual/forward-sequence.html">MPL sequence</a> which |
| can be used to specify the optional arguments to an <code>__init__</code> |
| function.</p> |
| |
| <h4><a name="optional-spec-synopsis"></a>Class template |
| <code>optional</code> synopsis</h4> |
| <pre> |
| namespace boost { namespace python |
| { |
| template <T1 = <i>unspecified</i>,...T<i>n</i> = <i>unspecified</i>> |
| struct optional {}; |
| }} |
| </pre> |
| |
| <h2><a name="examples"></a>Example(s)</h2> |
| |
| <p>Given the C++ declarations:</p> |
| <pre> |
| class Y; |
| class X |
| { |
| public: |
| X(int x, Y* y) : m_y(y) {} |
| X(double); |
| private: |
| Y* m_y; |
| }; |
| </pre> |
| A corresponding Boost.Python extension class can be created with: |
| <pre> |
| using namespace boost::python; |
| |
| class_<X>("X", "This is X's docstring.", |
| init<int,char const*>(args("x","y"), "X.__init__'s docstring")[ |
| with_custodian_and_ward<1,3>()] |
| ) |
| .def(init<double>()) |
| ; |
| </pre> |
| <hr> |
| Revised |
| <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> |
| 13 November, 2002 |
| <!--webbot bot="Timestamp" endspan i-checksum="39359" --> |
| |
| |
| <p><i>© Copyright <a href= |
| "http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2002.</i></p> |
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