casting

Returns the spellname if the UNIT is casting, otherwise false.

casting([UnitId]) : spellname : false
casting([UnitId]) : spellname : false 

1. See Wowpedia for more information on WoW Unit IDs. Will default to 'player' if nothing is specified.

Example

if casting('target') then 
  return cast(Rebuke, 'target')
end
if casting('target') then 
  return cast(Rebuke, 'target')
end 

if casting('target') == "Shadow Bolt" then 
  return cast(Rebuke, 'target')
end
if casting('target') == "Shadow Bolt" then 
  return cast(Rebuke, 'target')
end

if casting() then 
  return 
end
if casting() then 
  return 
end

Note

Just because it returns a spell does not mean it can be interrupted.