EC
TypeError
RubyERRORNotableType

Operation applied to wrong type

Quick Answer

Verify input types before operations; use .is_a? or explicit conversion methods like to_i, to_s.

What this means

Raised when an object is not of the expected type for an operation. Common in numeric coercion, type conversion failures, and operations that require a specific class.

Why it happens
  1. 1Adding incompatible types (e.g., String + Integer)
  2. 2Passing a non-hash where a hash is required
  3. 3Conversion methods receiving an object that cannot be coerced

Fix

Explicit type conversion

Explicit type conversion
value = params[:count]   # likely a String from HTTP
count = value.to_i       # safe coercion; returns 0 on failure
total = count + 10

Why this works

to_i, to_f, to_s perform best-effort conversions without raising TypeError.

Code examples
Reproducing the errorruby
"hello" + 42
# TypeError: no implicit conversion of Integer into String
Type guardruby
def double(n)
  raise TypeError, "Expected Numeric, got #{n.class}" unless n.is_a?(Numeric)
  n * 2
end
Rescue TypeErrorruby
begin
  result = value.to_str   # strict conversion
rescue TypeError => e
  result = value.to_s     # fallback
end
Sources
Official documentation ↗

Ruby Core Documentation

Content generated with AI assistance and reviewed for accuracy. Found an error? hello@errcodes.dev

← All Ruby errors