Module | Forwardable |
In: |
forwardable.rb
|
The Forwardable module provides delegation of specified methods to a designated object, using the methods def_delegator and def_delegators.
For example, say you have a class RecordCollection which contains an array @records. You could provide the lookup method record_number(), which simply calls #[] on the @records array, like this:
class RecordCollection extends Forwardable def_delegator :@records, :[], :record_number end
Further, if you wish to provide the methods size, #<<, and map, all of which delegate to @records, this is how you can do it:
class RecordCollection # extends Forwardable, but we did that above def_delegators :@records, :size, :<<, :map end
Also see the example at forwardable.rb.
debug | [RW] | force Forwardable to show up in stack backtraces of delegated methods |
Defines a method method which delegates to obj (i.e. it calls the method of the same name in obj). If new_name is provided, it is used as the name for the delegate method.
See the examples at Forwardable and forwardable.rb.
# File forwardable.rb, line 143 def def_instance_delegator(accessor, method, ali = method) accessor = accessor.id2name if accessor.kind_of?(Integer) method = method.id2name if method.kind_of?(Integer) ali = ali.id2name if ali.kind_of?(Integer) module_eval("def \#{ali}(*args, &block)\nbegin\n\#{accessor}.__send__(:\#{method}, *args, &block)\nrescue Exception\n$@.delete_if{|s| /^\\\\(__FORWARDABLE__\\\\):/ =~ s} unless Forwardable::debug\nKernel::raise\nend\nend\n", "(__FORWARDABLE__)", 1) end
Shortcut for defining multiple delegator methods, but with no provision for using a different name. The following two code samples have the same effect:
def_delegators :@records, :size, :<<, :map def_delegator :@records, :size def_delegator :@records, :<< def_delegator :@records, :map
See the examples at Forwardable and forwardable.rb.
# File forwardable.rb, line 130 def def_instance_delegators(accessor, *methods) for method in methods def_instance_delegator(accessor, method) end end