The AddMethod
function is used to add a method
to an environment. It's typically used to add a "pseudo-builder,"
a function that looks like a Builder
but
wraps up calls to multiple other Builder
s
or otherwise processes its arguments
before calling one or more Builder
s.
In the following example,
we want to install the program into the standard
/usr/bin directory hierarchy,
but also copy it into a local install/bin
directory from which a package might be built:
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
This produces the following:
% scons -Q / cc -o hello.o -c hello.c cc -o hello hello.o Install file: "hello" as "/usr/bin/hello" Install file: "hello" as "install/bin/hello"
As mentioned, a psuedo-builder also provides 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). This example also 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.
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 target = "%s/test_%s" % (testdir, testfile) if env['PLATFORM'] == 'win32': resfile = env.RES(resourcefile) p = env.Program(target, [srcfile, resfile]) else: p = env.Program(target, srcfile) return p AddMethod(Environment, BuildTestProg) env = Environment() env.BuildTestProg('stuff', resourcefile='res.rc')
This produces the following on Linux:
% scons -Q cc -o test_stuff.o -c test_stuff.c cc -o tests/test_stuff test_stuff.o
And the following on Windows:
C:\>scons -Q rc /fores.res res.rc cl /Fotest_stuff.obj /c test_stuff.c /nologo link /nologo /OUT:tests\test_stuff.exe test_stuff.obj res.res
Using AddMethod
is better than just adding an instance method
to a construction environment because it gets called as a proper method,
and because AddMethod
provides for copying the method
to any clones of the construction environment instance.