Class: Rewrite::Prelude::Try

Inherits:
SexpProcessor
  • Object
show all
Defined in:
lib/rewrite/prelude/try.rb

Overview

Adds a polite method invocation to Ruby:

with(try) do
  ...
  @phone = Location.find(:first, ...elided... ).try.phone
  ...
end

Based on “try()”:ozmm.org/posts/try.html by Chris Wanstrath

It also works with parameters, blocks, and procs passed as blocks.

Works by rewriting expressions like:

numbers.try(:sum)

Into:

lambda { |receiver, message|
  receiver.send message if receiver.respond_to? message
}.call(numbers, :sum)

See also: Please, Andand

Instance Method Summary collapse

Instance Method Details

#process_call(exp) ⇒ Object 



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# File 'lib/rewrite/prelude/try.rb', line 38

def process_call(exp)
  # [:call, [:dvar, :foo], :try, [:array, [:lit, :bar]]]
  exp.shift
  # [[:dvar, :foo], :try, [:array, [:lit, :bar]]]]
  receiver_sexp = exp.first
  if exp[1] == :try
    message_expression = exp[2][1]
    exp.clear
    s(:call, 
      s(:iter, 
        s(:fcall, :lambda), 
        s(:masgn,
          s(:array,
            s(:dasgn_curr, :receiver),
            s(:dasgn_curr, :message)
          )
        ), 
        s(:if, 
          s(:call, s(:dvar, :receiver), :respond_to?, s(:array, s(:dvar, :receiver))), 
          s(:call, s(:dvar, :receiver), :send, s(:array, s(:dvar, :message))),
          s(:nil)
        )
      ), 
      :call, 
      s(:array, 
        process_inner_expr(receiver_sexp), # [:dvar, :foo]
        process_inner_expr(message_expression)
      )
    )
  else
    # pass through
    begin
      s(:call,
        *(exp.map { |inner| process_inner_expr inner })
      )
    ensure
      exp.clear
    end
  end
end