WoW API: GetContainerNumSlots

Reference e
AddOns WoW API Widget API XML UI Event API WoW Lua Macro API CVars Battle.net HOWTOs Snippets UI tech Categories

Returns the total number of slots in the bag specified by the index.

numberOfSlots = GetContainerNumSlots(bagID);

Parameters[edit]

Integer - the slot containing the bag, e.g. 0 for backpack, etc.

numberOfSlots

Integer - the number of slots in the specified bag, or 0 if there is no bag in the given slot.

In 2.0.3, the Key Ring(-2) always returns 32. The size of the bag displayed is determined by the amount of space used in the keyring.
As of 3.0.3, immediately after a PLAYER_ENTERING_WORLD event (initial login or zone change through an instance, ie. any time you see a loading screen), several events of BAG_UPDATE are fired, one for each bag slot you have purchased. All bag data is available during the PLAYER_ENTERING_WORLD event, but this function returns 0 for bags that have not had the BAG_UPDATE function called. This is most likely due to the UI resetting its internal cache sometime between the PLAYER_ENTERING_WORLD event and the first BAG_UPDATE event. Also, that might be caused by the fact that some items (e.g. Ruby Essence from Oculus instance in Northrend) disappear from your bags when you're in the wrong zone.