Given a class, see if instance has method (Ruby)

Viewed 119517

I know in Ruby that I can use respond_to? to check if an object has a certain method.

But, given the class, how can I check if the instance has a certain method?

i.e, something like

Foo.new.respond_to?(:bar)

But I feel like there's gotta be a better way than instantiating a new instance.

12 Answers

While respond_to? will return true only for public methods, checking for "method definition" on a class may also pertain to private methods.

On Ruby v2.0+ checking both public and private sets can be achieved with

Foo.private_instance_methods.include?(:bar) || Foo.instance_methods.include?(:bar)

On my case working with ruby 2.5.3 the following sentences have worked perfectly :

value = "hello world"

value.methods.include? :upcase

It will return a boolean value true or false.

Related