▁compile ▁to ▁constants ▁in ▁the ▁executable , ▁these ▁liter als ▁compile ▁to ▁code ▁equivalent ▁to ▁the ▁above ▁method ▁calls . ▁In ▁particular , ▁under ▁manually ▁reference - count ed ▁memory ▁management , ▁these ▁objects ▁are ▁aut ore leased , ▁which ▁requires ▁added ▁care ▁when ▁e . g ., ▁used ▁with ▁function - static ▁variables ▁or ▁other ▁kinds ▁of ▁glob als . ▁ ▁Sub script ing ▁When ▁using ▁Apple ▁LL VM ▁compiler ▁ 4 . 0 ▁or ▁later , ▁arrays ▁and ▁diction aries ▁( NS Array ▁and ▁NS Dictionary ▁classes ) ▁can ▁be ▁manip ulated ▁using ▁sub script ing . ▁ ▁Sub script ing ▁can ▁be ▁used ▁to ▁retrieve ▁values ▁from ▁indexes ▁( array ) ▁or ▁keys ▁( dictionary ), ▁and ▁with ▁mutable ▁objects , ▁can ▁also ▁be ▁used ▁to ▁set ▁objects ▁to ▁indexes ▁or ▁keys . ▁In ▁code , ▁sub script ing ▁is ▁represented ▁using ▁brackets ▁[ ▁ ]. ▁ ▁Example ▁without ▁sub script ing : ▁ ▁id ▁object 1 ▁= ▁[ some Array ▁object AtIndex : 0 ]; ▁id ▁object 2 ▁= ▁[ some Dictionary ▁object ForKey :@" key "]; ▁[ some Mutable Array ▁replace Object AtIndex : 0 ▁with Object : object 3 ]; ▁[ some Mutable Dictionary ▁set Object : object 4 ▁for Key :@" key "]; ▁ ▁Example ▁with ▁sub script ing : ▁ ▁id ▁object 1 ▁= ▁some Array [ 0 ]; ▁id ▁object 2 ▁= ▁some Dictionary [ @" key "]; ▁some Mutable Array [ 0 ] ▁= ▁object 3 ; ▁some Mutable Dictionary [ @" key