Given a class, see if instance has method (Ruby)
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.
Answer
I don't know why everyone is suggesting you should be using instance_methods and include? when method_defined? does the job.
class Test
def hello; end
end
Test.method_defined? :hello #=> true
NOTE
In case you are coming to Ruby from another OO language OR you think that method_defined means ONLY methods that you defined explicitly with:
def my_method
end
then read this:
In Ruby, a property (attribute) on your model is basically a method also. So method_defined? will also return true for properties, not just methods.
For example:
Given an instance of a class that has a String attribute first_name:
<instance>.first_name.class #=> String
<instance>.class.method_defined?(:first_name) #=> true
since first_name is both an attribute and a method (and a string of type String).