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- forwardable.rb
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Forwardable
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 extend 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 # extend Forwardable, but we did that above def_delegators :@records, :size, :<<, :map end
Also see the example at forwardable.rb.
Attributes
Public Instance 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)
begin
#{accessor}.__send__(:#{method}, *args, &block)
rescue Exception
$@.delete_if{|s| /^\\(__FORWARDABLE__\\):/ =~ s} unless Forwardable::debug
Kernel::raise
end
end
", "(__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
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