method

returning

v2.2.1 - Show latest stable - 2 notes - Class: Object

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What's this?

returning(value) public

Returns value after yielding value to the block. This simplifies the process of constructing an object, performing work on the object, and then returning the object from a method. It is a Ruby-ized realization of the K combinator, courtesy of Mikael Brockman.

Examples

 # Without returning
 def foo
   values = []
   values << "bar"
   values << "baz"
   return values
 end

 foo # => ['bar', 'baz']

 # returning with a local variable
 def foo
   returning values = [] do
     values << 'bar'
     values << 'baz'
   end
 end

 foo # => ['bar', 'baz']

 # returning with a block argument
 def foo
   returning [] do |values|
     values << 'bar'
     values << 'baz'
   end
 end

 foo # => ['bar', 'baz']

Show source

# File activesupport/lib/active_support/core_ext/object/misc.rb, line 38
  def returning(value)
    yield(value)
    value
  end

January 8, 2009

5 thanks

Watch out for syntax errors

Watch out when you are using returning with hashes. If you would write code like

def foo(bars)
  returning {} do |map|
    bars.each { |bar| map[bar.first] = bar }
  end
end

you will get a syntax error since it looks like you tried to supply two blocks! Instead you should write it with parenthesis around the hash:

def foo(bars)
  returning({}) do |map|
    bars.each { |bar| map[bar.first] = bar }
  end
end

July 23, 2012

0 thanks

Replacement

# Method using returning can replaced
def foo
  returning Hash.new do |h|
    h[:foo] = "bar"
  end
end
# By method using tap  
def foo
  Hash.new.tap do |h|
    h[:foo] = "bar"
  end
end

returning

Related methods

Examples

Watch out for syntax errors

Replacement

Replacement