Refer to a method with varying name

Question

I'd like to know how to call a method with a varying name. I have:

queries = ['new_teachers']

I'd like to call the method new_teachers on a module DailyQueries using a reference to the array element like DailyQueries[queries[i]], which should be equivalent to DailyQueries.new_teachers. Any help greatly appreciated.

Answer 1

You can use the public_send method to call an arbitrary method on an object. For example, foo.public_send(:bar) is equivalent to foo.bar, and works exactly the same way.

Knowing this you can define an array of symbols, where each symbol is a method you want to call. So:

[:bar, :baz, :qorg].each {|method|
  DailyQueries.public_send(method)
end

will work the same as:

DailyQueries.bar
DailyQueries.baz
DailyQueries.qorg

Here's some reading material if you'd like to learn more about the public_send method, and its less privacy-respecting cousin, the send method:

• What is the difference between ruby send and ruby public_send method?
• What does send() do in Ruby?
• Object#public_send on RubyDoc

Answer 2

If you need just a way to call a method if a variable has method name string, then, refer to @sawa's answer. If, for some specific reason, you need to invoke a module method using [] syntax, then, read on.

---

If you say method is part of module, then, it must be its singleton method as shown below, only then, you can invoke it using DailyQueries.new_teachers syntax

module DailyQueries
  def self.new_teachers
    ["A", "B"]
  end
end

You cannot invoke module methods using [] syntax - hence, you may have to add a method to module that does this for you.

module DailyQueries
  def self.[] name, *params
    method(name)[*params]
  end
  #... other methods definitions
end

Now, you can do this:

DailyQueries[queries[0]]

If the method had any parameters, you can pass arguments as:

DailyQueries[queries[0], "param1", "param2", :another_param]

Answer 3

DailyQueries.send(queries[i])

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