What does "wrong number of arguments (1 for 0)" mean in Ruby?

When you define a function, you also define what info (arguments) that function needs to work. If it is designed to work without any additional info, and you pass it some, you are going to get that error.

Example: Takes no arguments:

def dog
end

Takes arguments:

def cat(name)
end

When you call these, you need to call them with the arguments you defined.

dog                  #works fine
cat("Fluffy")        #works fine


dog("Fido")          #Returns ArgumentError (1 for 0)
cat                  #Returns ArgumentError (0 for 1)

Check out the Ruby Koans to learn all this.

You passed an argument to a function which didn't take any. For example:

def takes_no_arguments
end

takes_no_arguments 1
# ArgumentError: wrong number of arguments (1 for 0)

I assume you called a function with an argument which was defined without taking any.

def f()
  puts "hello world"
end

f(1)   # <= wrong number of arguments (1 for 0)