Move %attribute documentation into the manual
It's fairly hidden where it is, put it where users can see it more easily. Fixes #2166
This commit is contained in:
Corey Minyard
parent
07f5b37c30
commit
f77af57bd7
3 changed files with 212 additions and 131 deletions
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@ -184,6 +184,7 @@
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<li><a href="SWIG.html#SWIG_nn32">Typedef and structures</a>
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<li><a href="SWIG.html#SWIG_nn33">Character strings and structures</a>
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<li><a href="SWIG.html#SWIG_nn34">Array members</a>
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<li><a href="SWIG.html#Attributes">Attributes and the %attribute directive</a>
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<li><a href="SWIG.html#SWIG_structure_data_members">Structure data members</a>
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<li><a href="SWIG.html#SWIG_nn36">C constructors and destructors</a>
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<li><a href="SWIG.html#SWIG_adding_member_functions">Adding member functions to C structures</a>
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@ -59,6 +59,7 @@
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<li><a href="#SWIG_nn32">Typedef and structures</a>
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<li><a href="#SWIG_nn33">Character strings and structures</a>
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<li><a href="#SWIG_nn34">Array members</a>
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<li><a href="#Attributes">Attributes and the %attribute directive</a>
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<li><a href="#SWIG_structure_data_members">Structure data members</a>
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<li><a href="#SWIG_nn36">C constructors and destructors</a>
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<li><a href="#SWIG_adding_member_functions">Adding member functions to C structures</a>
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@ -2635,7 +2636,212 @@ discussed in a later chapter. In many cases, the warning message is
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harmless.
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</p>
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<H3><a name="SWIG_structure_data_members">5.5.4 Structure data members</a></H3>
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<H3><a name="Attributes">5.5.4 Attributes and the %attribute directive</a></H3>
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<p>
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Use <tt>%attribute</tt> when you have a pair of get/set methods to a
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primitive type like in:
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</p>
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<div class="code">
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<pre>
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%attribute(A, int, a, get_a, set_a);
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struct A
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{
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int get_a() const;
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void set_a(int aa);
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};
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</pre>
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</div>
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<p>
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and you want to provide that variable as an attribute in the target
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langage. This examples only works for primitive types, not derived
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types. If you don't provide a 'set' method, a 'read-only' attribute
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is generated, ie, like in:
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</p>
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<div class="code">
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<pre>
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%attribute(A, int, c, get_c);
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</pre>
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</div>
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<p>
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Use <tt>%attributeref</tt> when you have const/non-const reference
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access methods for primitive types or class/structs, like in:
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</p>
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<div class="code">
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<pre>
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%attributeref(A, int, b);
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struct A
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{
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const int& b() const;
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int& b();
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};
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%attributeref(B, int, c);
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struct B
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{
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int& c();
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};
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</pre>
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</div>
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<p>
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You can also use
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</p>
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<div class="code">
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<pre>
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%attributeref(Class, AttributeType, AttributeName, AccessorMethod)
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</pre>
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</div>
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<p>
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if the internal C++ reference methods have a different name from the
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attribute you want, so
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</p>
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<div class="code">
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<pre>
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%attributeref(B, int, d, c);
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</pre>
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</div>
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<p>
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is the same as the last example, but instead of the attribute 'c' being
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called 'c', it is called 'd'.
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</p>
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<p>
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Now you can use the attributes like so:
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</p>
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<div class="code">
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<pre>
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x = A()
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x.a = 3 # calls A::set_a
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print x.a # calls A::get_a
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x.b = 3 # calls A::b()
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print x.b # calls A::b() const
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</pre>
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</div>
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<p>
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Use <tt>%attribute2</tt> instead of <tt>%attribute</tt> to indicate
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that reference-pointer translation is required. You
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use <tt>%attribute2</tt> instead of <tt>%attribute</tt> in cases like
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this:
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</p>
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<div class="code">
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<pre>
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%attribute2(MyClass, MyFoo, Foo, GetFoo, SetFoo);
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%inline %{
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struct MyFoo {
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int x;
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};
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class MyClass {
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MyFoo foo;
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public:
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MyFoo& GetFoo() { return foo; }
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void SetFoo(const MyFoo& other) { foo = other; }
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};
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%}
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</pre>
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</div>
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<p>
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Here, the data type of the property is a wrapped type (MyFoo) and on
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the C++ side it is passed by reference. The problem is that the SWIG
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wrapper will pass around a pointer (MyFoo *) which is not compatible
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with the reference type of the accessors (MyFoo &). Therefore, if you
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use <tt>%attribute</tt>, you'll get an error from your C/C++
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compiler. <tt>%attribute2</tt> translates between a pointer and a
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reference to eliminate the error. In case you're confused, let's make
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it simple: just use <tt>%attribute</tt> at first, but if the C/C++
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compiler gives an error while compiling the wrapper,
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try <tt>%attribute2</tt> instead.
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</p>
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<p>
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NOTE: remember that if the type contains commas, such as
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'std::pair<int,int>', you need to use the macro like:
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</p>
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<div class="code">
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<pre>
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%attributeref(A, %arg(std::pair<int,int>), pval);
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</pre>
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</div>
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<p>
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where <tt>%arg()</tt> 'normalizes' the type to be understood as a single
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argument, otherwise the macro will get confused by the comma.
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</p>
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<p>
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The <tt>%attributeval</tt> is the same as <tt>%attribute</tt>, but
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should be used when the type is a class/struct (ie a non-primitive
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type) and when the get and set methods return/pass by value. The
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following is very similar to the above example, but note that the
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access is by value rather than reference.
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</p>
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<div class="code">
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<pre>
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%attributeval(MyClassVal, MyFoo, ReadWriteFoo, GetFoo, SetFoo);
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%attributeval(MyClassVal, MyFoo, ReadOnlyFoo, GetFoo);
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%inline %{
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class MyClassVal {
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MyFoo foo;
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public:
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MyFoo GetFoo() { return foo; }
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void SetFoo(MyFoo other) { foo = other; }
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};
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%}
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</pre>
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</div>
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<p>
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The <tt>%attributestring</tt> is the same as <tt>%attributeval</tt>,
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but should be used for string class types, which are unusual as they
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are a class on the C++ side, but normally an immutable/primitive type
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in the target language. Example usage for std::string:
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</p>
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<div class="code">
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<pre>
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%include <std_string.i>
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%attributestring(MyStringyClass, std::string, ReadWriteString, GetString, SetString);
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%attributestring(MyStringyClass, std::string, ReadOnlyString, GetString);
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%inline %{
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class MyStringyClass {
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std::string str;
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public:
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MyStringyClass(const std::string &val) : str(val) {}
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std::string GetString() { return str; }
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void SetString(std::string other) { str = other; }
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};
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%}
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</pre>
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</div>
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<p>
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The <tt>%attributestring</tt> also works for class types that
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have <tt>%naturalvar</tt> turned on and so is also useful for
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shared_ptr which has <tt>%naturalvar</tt> turned on in
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<tt>%shared</tt>_ptr.
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</p>
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<H3><a name="SWIG_structure_data_members">5.5.5 Structure data members</a></H3>
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<p>
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@ -2741,7 +2947,7 @@ class, or union. This is unlikely to break existing code. However, if you need
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datatype is really a struct, simply use a forward struct declaration such as <tt>"struct Foo;"</tt>.
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</p>
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<H3><a name="SWIG_nn36">5.5.5 C constructors and destructors</a></H3>
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<H3><a name="SWIG_nn36">5.5.6 C constructors and destructors</a></H3>
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<p>
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@ -2830,7 +3036,7 @@ the target languages, and it is highly recommended you don't use them.
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</p>
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<H3><a name="SWIG_adding_member_functions">5.5.6 Adding member functions to C structures</a></H3>
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<H3><a name="SWIG_adding_member_functions">5.5.7 Adding member functions to C structures</a></H3>
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<p>
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@ -3103,7 +3309,7 @@ be used to extend a structure with more than just methods, a more suitable
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directive name has been chosen.
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</p>
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<H3><a name="SWIG_nested_structs">5.5.7 Nested structures</a></H3>
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<H3><a name="SWIG_nested_structs">5.5.8 Nested structures</a></H3>
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<p>
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@ -3187,7 +3393,7 @@ Finally, note that nesting is handled differently in C++ mode,
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see <a href="SWIGPlus.html#SWIGPlus_nested_classes">Nested classes</a>.
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</p>
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<H3><a name="SWIG_nn39">5.5.8 Other things to note about structure wrapping</a></H3>
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<H3><a name="SWIG_nn39">5.5.9 Other things to note about structure wrapping</a></H3>
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<p>
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@ -7,132 +7,6 @@
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/*
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The following macros convert a pair of set/get methods
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into a "native" attribute.
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Use %attribute when you have a pair of get/set methods to a primitive type
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like in:
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%attribute(A, int, a, get_a, set_a);
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struct A
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{
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int get_a() const;
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void set_a(int aa);
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};
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If you don't provide a 'set' method, a 'read-only' attribute
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is generated, ie, like in:
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%attribute(A, int, c, get_c);
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Use %attributeref when you have const/non-const reference access methods
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for primitive types or class/structs, like in:
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%attributeref(A, int, b);
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struct A
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{
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const int& b() const;
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int& b();
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};
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%attributeref(B, int, c);
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struct B
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{
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int& c();
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};
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You can also use
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%attributeref(Class, AttributeType, AttributeName, AccessorMethod)
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if the internal C++ reference methods have a different name from the
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attribute you want, so
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%attributeref(B, int, d, c);
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is the same as the last example, but instead of the attribute 'c' being
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called 'c', it is called 'd'.
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Now you can use the attributes like so:
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x = A()
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x.a = 3 # calls A::set_a
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print x.a # calls A::get_a
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x.b = 3 # calls A::b()
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print x.b # calls A::b() const
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Use %attribute2 instead of %attribute to indicate that reference-pointer
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translation is required. You use %attribute2 instead of %attribute in
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cases like this:
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%attribute2(MyClass, MyFoo, Foo, GetFoo, SetFoo);
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%inline %{
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struct MyFoo {
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int x;
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};
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class MyClass {
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MyFoo foo;
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public:
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MyFoo& GetFoo() { return foo; }
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void SetFoo(const MyFoo& other) { foo = other; }
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};
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%}
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Here, the data type of the property is a wrapped type (MyFoo) and on the
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C++ side it is passed by reference. The problem is that the SWIG wrapper will
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pass around a pointer (MyFoo *) which is not compatible with the reference
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type of the accessors (MyFoo &). Therefore, if you use %attribute, you'll get
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an error from your C/C++ compiler. %attribute2 translates between a pointer
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and a reference to eliminate the error. In case you're confused, let's make it
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simple: just use %attribute at first, but if the C/C++ compiler gives an error
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while compiling the wrapper, try %attribute2 instead.
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NOTE: remember that if the type contains commas, such as 'std::pair<int,int>',
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you need to use the macro like:
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%attributeref(A, %arg(std::pair<int,int>), pval);
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where %arg() 'normalizes' the type to be understood as a single
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argument, otherwise the macro will get confused by the comma.
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The %attributeval is the same as %attribute, but should be used when the type
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is a class/struct (ie a non-primitive type) and when the get and set methods
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return/pass by value. The following is very similar to the above example, but
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note that the access is by value rather than reference.
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%attributeval(MyClassVal, MyFoo, ReadWriteFoo, GetFoo, SetFoo);
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%attributeval(MyClassVal, MyFoo, ReadOnlyFoo, GetFoo);
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%inline %{
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class MyClassVal {
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MyFoo foo;
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public:
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MyFoo GetFoo() { return foo; }
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void SetFoo(MyFoo other) { foo = other; }
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};
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%}
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The %attributestring is the same as %attributeval, but should be used for string
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class types, which are unusual as they are a class on the C++ side, but normally an
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immutable/primitive type in the target language. Example usage for std::string:
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%include <std_string.i>
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%attributestring(MyStringyClass, std::string, ReadWriteString, GetString, SetString);
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%attributestring(MyStringyClass, std::string, ReadOnlyString, GetString);
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%inline %{
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class MyStringyClass {
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std::string str;
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public:
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MyStringyClass(const std::string &val) : str(val) {}
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std::string GetString() { return str; }
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void SetString(std::string other) { str = other; }
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};
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%}
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The %attributestring also works for class types that have %naturalvar turned
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on and so is also useful for shared_ptr which has %naturalvar turned on in %shared_ptr.
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*/
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//
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