TypeError

TypeError is raised when an object is not of the expected type. This happens when Ruby can't implicitly convert one type to another, or when an operation is incompatible with the object's type.

Common causes

• Trying to concatenate incompatible types (String + Integer)
• Passing wrong type to a method expecting specific type
• Using nil where an object is expected
• Array/Hash operations on wrong types
• Implicit conversion failures

How to fix it

• Explicitly convert types: value.to_s, value.to_i
• Use string interpolation instead of concatenation
• Validate types before operations
• Check for nil before type-specific operations
• Use duck typing checks: respond_to?(:method_name)

Example

# Error example
"Age: " + 25  # => TypeError: no implicit conversion of Integer into String

# Fix with explicit conversion
"Age: " + 25.to_s  # => "Age: 25"

# Or use interpolation
"Age: #{25}"  # => "Age: 25"

Related errors