Source

SCons / doc / user / add-method.in

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  <para>

  The env.AddMethod(function, [name]) function is used to add a method
  to an environment.  It's typically used to add a "pseudo-builder" or
  wrap up a call to multiple builders.  In the first example, we want
  to install the program into the standard bin dir, but also copy it
  into a local install/bin dir that might be used to build a package
  from.

  </para>

  <scons_example name="ex1">
     <file name="SConstruct" printme="1">
     def install_in_bin_dirs(env, source):
         """Install source in both bin dirs"""
         i1 = env.Install("$BIN", source)
         i2 = env.Install("$LOCALBIN", source)
         return [i1[0], i2][0] # Return a list, like a normal builder
     env = Environment(BIN='/usr/bin', LOCALBIN='#install/bin')
     env.AddMethod(install_in_bin_dirs, "InstallInBinDirs")
     env.InstallInBinDirs(Program('hello.c')) # installs hello in both bin dirs     
     </file>
     <file name="hello.c">
     int main() { printf("Hello, world!\n"); }
     </file>
  </scons_example>

  <para>
  This produces the following:
  </para>

  <scons_output example="ex1">
    <scons_output_command>scons -Q</scons_output_command>
  </scons_output>

  <para>

  It also gives more flexibility in parsing arguments than you can get
  with a builder.  The next example shows a pseudo-builder with a
  named argument that modifies the filename, and a separate argument
  for the resource file (rather than having the builder figure it out
  by file extension).  Also this example demonstrates using the global
  AddMethod function to add a method to the global Environment class,
  so it will be used in all subsequently created environments.

  </para>

  <scons_example name="ex2">
     <file name="SConstruct" printme="1">
     import sys
     def BuildTestProg(env, testfile, resourcefile, testdir="tests"):
         """Build the test program;
         prepends "test_" to src and target, and puts target into testdir."""
         srcfile="test_%s.c"%testfile
         if sys.platform=='win32':
             target="%s/test_%s$EXESUFFIX"%(testdir,[testfile, resourcefile])
         else:
             target="%s/test_%s$EXESUFFIX"%(testdir,testfile)
         p = env.Program(target, srcfile)
         return p
     AddMethod(Environment, BuildTestProg)

     # Now use it
     env=Environment()
     env.BuildTestProg('stuff', resourcefile='res.rc')
     </file>
     <file name="test_stuff.c">
     int main() { printf("Hello, world!\n"); }
     </file>
  </scons_example>

  <para>
  This produces the following (on Linux, anyway; Windows would include the
  resource file):
  </para>

  <scons_output example="ex2">
    <scons_output_command>scons -Q</scons_output_command>
  </scons_output>

  <para>
  Using AddMethod is better than just adding an instance method to an
  Environment because it gets called as a proper method, and AddMethod
  provides for copying the method to any copies of the Environment
  instance.
  </para>