The association between feature names and methods is many-to-many, which means that a method may be involved in several features, and that a feature may be bound to several methods.
Here is how to create and use a new feature named foo:
from waflib.TaskGen import feature @feature('foo') def print_hello(self): print("Hello, World!")
The function print_hello is now associated with the waflib.TaskGen.task_gen class, which means that it may be used directly:
def build(bld): tg = bld() tg.print_hello()
The method may be called directly, and several times. If a method creates task, the same tasks will be created more than once, which may cause build errors. The feature attribute is used to have the associated methods called exactly once before the build starts:
def build(bld): bld(features='foo')
Here is a more complete example with two methods:
from waflib.TaskGen import feature, after_method @feature('foo') @after_method('print_bar') def print_hello(self): print("Hello, Foo!") @feature('bar') def print_bar(self): print("Hello, Bar!") def build(bld): bld(features='foo bar')
The order of method execution is unrelated to the order of the features given. For instance, this example will print “Hello, Bar!” then “Hello, Foo!”. The decorators waflib.TaskGen.after() and waflib.TaskGen.before() are enforcing partial order constraints on the methods to execute.
The following maps represent the associations betwen feature methods (represented in yellow) and methods associated to other feature names.