/trunk/Examples/go/variables/index.html
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- <html>
- <head>
- <title>SWIG:Examples:go:variables</title>
- </head>
- <body bgcolor="#ffffff">
- <tt>SWIG/Examples/go/variables/</tt>
- <hr>
- <H2>Wrapping C Global Variables</H2>
- <p>
- When a C global variable appears in an interface file, SWIG provides
- getter and setter functions for the variable. The getter function is
- named <tt>Get</tt> followed by the capitalized name of the variable.
- The setter variable starts with <tt>Set</tt> instead. The getter
- function takes no parameters and returns the value of the variable.
- The setter function takes a single parameter with the same type as the
- variable, and returns nothing.
- <p>Click <a href="example.i">here</a> to see a SWIG interface with
- some variable declarations in it.
- <h2>Manipulating Variables from Go</h2>
- For example, if the package is called <tt>example</tt>, the global
- variable
- <blockquote>
- <pre>
- double foo;
- </pre>
- </blockquote>
- will be accessed from Go as
- <blockquote>
- <pre>
- example.GetFoo();
- example.SetFoo(12.3);
- </pre>
- </blockquote>
- Click <a href="runme.go">here</a> to see the example program that
- updates and prints out the values of the variables using this
- technique.
- <h2>Key points</h2>
- <ul>
- <li>The name of the variable is capitalized.
- <li>When a global variable has the type "<tt>char *</tt>", SWIG
- manages it as a character string.
- <li><tt>signed char</tt> and <tt>unsigned char</tt> are handled as
- small 8-bit integers.
- <li>String array variables such as '<tt>char name[256]</tt>' are
- managed as Go strings, but when setting the value, the result is
- truncated to the maximum length of the array. Furthermore, the string
- is assumed to be null-terminated.
- <li>When structures and classes are used as global variables, they are
- mapped into pointers. Getting the "value" returns a pointer to the
- global variable. Setting the value of a structure results in a memory
- copy from a pointer to the global.
- </ul>
- <h2>Creating read-only variables</h2>
- The <tt>%immutable</tt> and <tt>%mutable</tt> directives can be used
- to specify a collection of read-only variables. A read only variable
- will have a getter function but no setter function. For example:
- <blockquote>
- <pre>
- %immutable;
- int status;
- double blah;
- ...
- %mutable;
- </pre>
- </blockquote>
- The <tt>%immutable</tt> directive remains in effect until it is
- explicitly disabled using the <tt>%mutable</tt> directive.
- </body>
- </html>
- <hr>