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Contents
# coding: utf-8
# This module defines class methods, with which the host class of FlexProxy
# is to be extended.
#
module FlexCoerce::ClassMethods
# Class method .coercion_table provides access to the table of coercion
# behavior specific to each host class. The table itself is a hash with
# method names as keys. Each value is an array of pairs [ type, block ],
# where type specifies the operand type, and block specifies the behavior
# when the method in question is invoked with the given operand type.
#
def coercion_table
@coercion_table ||= Hash.new { |hash, missing_key|
case missing_key
when Symbol then hash[ missing_key ] = []
else
hash[ missing_key.to_sym ]
end
}
end
# Class method .define_coercion allows the classes that use FlexCoerce to
# define custom coercion for certain symbols. The method expects: (1)
# object type (or a list of object types), (2) +:method+ parameter
# specifying the method(s) for which coercion is being defined, and (3) a
# block that defines the operation. The block should take 2 ordered
# arguments, representing first and second operand. The first operand is
# the object that invoked #coerce method, the second operand is an
# instance of the receiver class. Example:
#
# define_coercion Integer, method: :* do |operand1, operand2|
# operand2 * operand1 # swap the operands
# end
#
def define_coercion *types,
method: fail( ArgumentError, "When defining coercion, " +
"method must be given!" ),
&block
unless block.arity == 2
fail ArgumentError, "The supplied block, which defines operation" +
"#{method}, must take exactly 2 arguments!"
end
# For each type, add one line to the coercion_table entry.
types.each do |type|
coercion_table[ method ] << [ type, block ]
end
end
end
Version data entries
6 entries across 6 versions & 1 rubygems