`send` alternative for lambda in Ruby

Question

send does not work for lambda in Ruby:

>> def mymethod; end
=> :mymethod
>> send('mymethod')
=> nil

>> mylambda = ->{}
=> #<Proc:0x9f2fe28@(pry):136 (lambda)>
>> send('mylambda')
=> NoMethodError: undefined method `mylambda' for main:Object

How do I dynamically call a lambda via a string?

Answer 1

You can't access local variables by name without using eval.

Here are a few alternatives you could try:

• Storing the lambda in a Hash:

  hash = {
    'mylambda' => ->{ 'foo' }
  }
  hash['mylambda'].call # => "foo"
  

• Storing the lambda in an instance variable:

  @mylambda = ->{ 'foo' }
  instance_variable_get('@mylambda').call # => "foo"
  

• Creating a temporary method using the lambda

  mylambda = ->{ 'foo' }
  define_method :temp, &mylambda
  send(:temp) # => "foo"
  

Answer 2

If you have the correct Binding for the context of your local variable, you can use Binding#local_variable_get to get the value of the local variable. And to get a Binding for the current context, you can use Kernel#binding:

binding.local_variable_get(:mylambda).()

Answer 3

You cant use send to invoke lambda. But you can use eval('mylambda').call to invoke

Answer 4

To invoke a lambda method you can either

mylambda.call
# => nil

or

mylambda.()
# => nil

---

If you want to call the lambda using a string as its variable name you can't - see here for alternatives of how to get other references by their names)