EC
ArgumentError
RubyERRORNotableArgument

Wrong number or type of arguments

Quick Answer

Check the method signature for required vs optional parameters and validate argument values before passing them.

What this means

Raised when a method receives the wrong number of arguments, or when an argument value is invalid for the method. It covers both arity mismatches and semantic validation failures.

Why it happens
  1. 1Passing too many or too few arguments to a method
  2. 2Passing an argument of the wrong value (e.g., negative where positive is required)
  3. 3Calling Integer() or Float() with a non-numeric string

Fix

Match the method arity

Match the method arity
def greet(name, greeting = 'Hello')
  "#{greeting}, #{name}!"
end

greet('Alice')           # OK
greet('Alice', 'Hi')    # OK
# greet()               # ArgumentError: wrong number of arguments (given 0, expected 1+)

Why this works

Default parameters reduce required arity; keyword arguments with defaults are even more flexible.

Code examples
Arity mismatchruby
def add(a, b)
  a + b
end
add(1)   # ArgumentError: wrong number of arguments (given 1, expected 2)
Invalid valueruby
Integer('abc')
# ArgumentError: invalid value for Integer(): "abc"
Rescuing ArgumentErrorruby
begin
  Integer(params[:age])
rescue ArgumentError
  puts 'Age must be a valid integer'
end
Sources
Official documentation ↗

Ruby Core Documentation

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