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<title>Advanced type conversion</title> |
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<h1>Advanced type conversion</h1> |
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<p>It is frequently useful to extend Pyd's type conversion mechanisms. The usual way to do this is to wrap classes or structs. Pyd has two additional mechanisms for more complex situations.</p> |
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<dl> |
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<dt><code>void d_to_python(<span class="t_arg">dg_t</span>) (<span class="t_arg">dg_t</span> <span class="arg">dg</span>);</code></dt> |
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<dd>This allows the user to define a function for returning a D type to Python. The <span class="arg">dg</span> may be either a function pointer or a delegate. The argument to the function pointer is of the type to convert. The return type of the function pointer can be any convertible type.</dd> |
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<dt><code>void python_to_d(<span class="t_arg">dg_t</span>) (<span class="t_arg">dg_t</span> <span class="arg">dg</span>);</code></dt> |
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<dd>This allows the user to define a function for converting a Python object to a D type. The <span class="arg">dg</span> may be either a function pointer or a delegate. The argument to the function pointer can be any convertible type. The return type of the function pointer is the type to convert.</dd> |
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</dl> |
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<p>Conversion functions defined with either of the above functions only take effect if Pyd's regular type conversion mechanisms fail. This would usually happen if a wrapped function returns or has a parameter of some un-wrapped class or struct type.</p> |
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<h3><a class="anchor" name="examples">Examples</a></h3> |
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<pre class="code"><span class="keyword">import</span> std.stdio; |
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<span class="keyword">struct</span> S { |
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<span class="keyword">int</span> i; |
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} |
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S foo() { |
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S s; |
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s.i = <span class="number">12</span>; |
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} |
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<span class="keyword">void</span> bar(S s) { |
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writefln(s); |
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} |
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<span class="keyword">extern</span> (C) <span class="keyword">void</span> PydMain() { |
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d_to_python(<span class="keyword">delegate int</span>(S s) { <span class="keyword">return</span> s.i; }); |
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python_to_d(<span class="keyword">delegate</span> S(<span class="keyword">int</span> i) { S s; s.i = i; <span class="keyword">return</span> s; }); |
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def!(foo); |
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def!(bar); |
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module_init(); |
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}</pre> |
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<p>And in Python:</p> |
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<pre class="code">>>> foo() |
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12 |
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>>> bar(<span class="number">20</span>) |
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20</pre> |
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