EC
UncaughtThrowError
RubyERRORNotableControl Flow

throw called with no matching catch

Quick Answer

Ensure every throw(:symbol) has a corresponding catch(:symbol) enclosing it in the call stack.

What this means

Raised when throw is called with a symbol for which there is no enclosing matching catch block. throw/catch in Ruby are a non-exception control flow mechanism, distinct from raise/rescue.

Why it happens
  1. 1throw :done called outside any catch :done block
  2. 2Mismatched throw/catch symbol names (typo)

Fix

Wrap with matching catch

Wrap with matching catch
result = catch(:found) do
  data.each do |item|
    throw :found, item if item.matches?(query)
  end
  nil   # default if not found
end

Why this works

catch(:found) creates the landing point for throw :found, returning the thrown value.

Code examples
Reproducing the errorruby
throw :done
# UncaughtThrowError: uncaught throw :done
Correct catch/throw usageruby
catch(:exit) do
  [1,2,3].each { |n| throw :exit, n if n == 2 }
end   # => 2
Rescue UncaughtThrowErrorruby
begin
  throw :missing_catch
rescue UncaughtThrowError => e
  puts "No catch for: #{e.tag}"
end
Sources
Official documentation ↗

Ruby Core Documentation

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