Module: ParamAccessor

Included in:
CommonParams, Rubylet::WarTask, RubyletDescriptor, StaticFileFilter
Defined in:
lib/rubylet/war_task.rb

Instance Method Summary collapse

Instance Method Details

#param_accessor(sym, default = nil, &block) ⇒ Object

Define a ‘param’, like attr_accessor, but with an optional default value. If params are defined as objects that respond to :call (e.g. a Proc) or a block is given, the proc or block will be instance_eval’ed in the context of the instance once on first read, after which the value is cached and returned on subsequent reads.



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# File 'lib/rubylet/war_task.rb', line 18

def param_accessor(sym, default = nil, &block)
  if !default.nil? && block_given?
    raise ArgumentError, 'both default value and block may not be given'
  end

  iv = "@#{sym}"
  define_method(sym) do
    v = instance_variable_get(iv)
    val = if !v.nil?
            v
          elsif !default.nil?
            default
          elsif block_given?
            block
          else
            nil
          end

    if val.respond_to?(:call)
      newval = instance_eval(&val)
      instance_variable_set(iv, newval)
      newval
    else
      val
    end
  end

  define_method("#{sym}=") do |val|
    instance_variable_set(iv, val)
  end
end