Warning¶

Sapphire uses structured warnings. This allows you to enable or disable warnings either globally or within a block. It also makes warnings testable.

Synopsis¶

You "raise" a warning the same way you raise an exception. The difference is that warnings don't break control flow, and aren't rescuable. They are informational only.

class Foo
  def old_method
    warn DeprecatedWarning, "this method is old" 
    # some old code...
  end
end

A warn call without a specific class raises a StandardWarning

class Foo
  def old_method
    warn "this method is old" # No warning class defaults to StandardWarning
  end
end

Disabling Warnings¶

A Warning class can be disabled locally or globally. If a block is provided, the warning is disabled only within the scope of that block. Otherwise, it is disabled at the point of the call.

# Disable globally
DeprecatedWarning.disable

# Disable within code block
DeprecatedWarning.disable do
  # Ignore deprecation warnings within this block
end

Advantages¶

1. Better control. No more "on" vs "off".
2. Better information. You can get backtrace information.
3. Testable. Both that a warning is raised, and the warning message.

Article¶

http://www.oreillynet.com/ruby/blog/2008/02/structured_warnings_now.html