Module: FlexCoerce::ClassMethods

Defined in:
lib/y_support/flex_coerce/class_methods.rb

Overview

This module defines class methods, with which the host class of FlexProxy is to be extended.

Instance Method Summary collapse

Instance Method Details

#coercion_table ⇒ Object

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.



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# File 'lib/y_support/flex_coerce/class_methods.rb', line 13

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

#define_coercion(*types, method: fail( ArgumentError, "When defining coercion, " + "method must be given!" ), &block) ⇒ Object

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



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# File 'lib/y_support/flex_coerce/class_methods.rb', line 36

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