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Documentation for csdirectorin 'pre', 'post' and 'terminator' support.

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Vladimir Kalinin 2013-01-11 21:46:40 +04:00 • committed by William S Fulton
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Doc/Manual/CSharp.html
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@ -197,11 +197,56 @@ csattributes C# attributes for attaching to proxy classes/enums
The "null" attribute in the "out" typemap can be specified to provide a value for <tt>$null</tt> to expand into for wrapped functions that return non-void. Normally the default value of <tt>0</tt> is used.
For example this is needed if you change the return type to void:
</p>
<div class="code"><pre>
%typemap(ctype) Status "void"
%typemap(out, null="") Status { ... }
</pre></div>
<p>
The "pre" and "post" attributes in "csdirectorin" typemap act like the same attributes in "csin" typemap.
For example if we modify <a href="#CSharp_date_marshalling">Date marshalling example</a> like this:
<div class="code"><pre>
class CDate {
...
void setYear(int);
void setMonth(int);
void setDay(int);
};
struct Action {
virtual void someCallback(CDate& date);
...
};
</pre></div>
and declare %feature ("director") for the Action class, we would have to define additional
marshaling rules for CDate. Director typemap may look like this:
<div class="code"><pre>
%typemap(csdirectorin,
pre="System.DateTime temp$iminput = new System.DateTime();",
post="CDate temp2$iminput = new CDate($iminput, false);\n"
"temp2$iminput.setYear(tempdate.Year);\n"
"temp2$iminput.setMonth(tempdate.Month);\n"
"temp2$iminput.setDay(tempdate.Day);"
) CDate& date "out temp$iminput"
</pre></div>
The generated proxy class code will then contain the following wrapper for calling user-overloaded someCallback():
<div class="code"><pre>
...
private void SwigDirectorsomeCallback(IntPtr date) {
System.DateTime tempdate = new System.DateTime();
try {
someCallback(out tempdate);
}
finally {
// we create managed wrapper around existing C reference, just for convenience
CDate temp2date = new CDate(date, false);
temp2date.setYear(tempdate.Year);
temp2date.setMonth(tempdate.Month);
temp2date.setDay(tempdate.Day);
}
}
...
</pre></div>
Pay special attention to the memory management issues, using these attributes.
</p>
</li>