In Ruby, we can check if a hash includes a key using the include? method. The include? method returns a boolean value true if the hash includes the given key, and false otherwise. Here is an example:
# Define a hash
my_hash = { name: "John", age: 30, city: "New York" }
# Check if the hash includes a key
puts my_hash.include?(:name) #=> true
puts my_hash.include?(:address) #=> false
In the above example, we define a hash my_hash with three key-value pairs. We then call the include? method on my_hash object twice to check if the hash includes the keys :name and :address. The first call returns true since :name key is present in the hash, while the second call returns false since :address key is not present in the hash.