▁dynamic ▁( late ) ▁binding .) ▁ ▁Inter faces ▁and ▁implementations ▁Object ive - C ▁requires ▁that ▁the ▁interface ▁and ▁implementation ▁of ▁a ▁class ▁be ▁in ▁separately ▁declared ▁code ▁blocks . ▁By ▁convention , ▁developers ▁place ▁the ▁interface ▁in ▁a ▁header ▁file ▁and ▁the ▁implementation ▁in ▁a ▁code ▁file . ▁The ▁header ▁files , ▁normally ▁suff ixed ▁. h , ▁are ▁similar ▁to ▁C ▁header ▁files ▁while ▁the ▁implementation ▁( method ) ▁files , ▁normally ▁suff ixed ▁. m , ▁can ▁be ▁very ▁similar ▁to ▁C ▁code ▁files . ▁ ▁Interface ▁This ▁is ▁analog ous ▁to ▁class ▁declarations ▁as ▁used ▁in ▁other ▁object - orient ed ▁languages , ▁such ▁as ▁C ++ ▁or ▁Python . ▁ ▁The ▁interface ▁of ▁a ▁class ▁is ▁usually ▁defined ▁in ▁a ▁header ▁file . ▁A ▁common ▁convention ▁is ▁to ▁name ▁the ▁header ▁file ▁after ▁the ▁name ▁of ▁the ▁class , ▁e . g . ▁ ▁would ▁contain ▁the ▁interface ▁for ▁the ▁class ▁. ▁ ▁An ▁interface ▁declaration ▁takes ▁the ▁form : ▁@ interface ▁class name ▁: ▁super class name ▁{ ▁ ▁// ▁instance ▁variables ▁} ▁+ ▁class Method 1 ; ▁+ ▁( return _ type ) class Method 2 ; ▁+ ▁( return _ type ) class Method 3 :( param 1 _ type ) param 1 _ var Name ; ▁ ▁- ▁( return _ type ) instance Method 1 With 1 Parameter :( param 1 _ type ) param 1 _ var Name ; ▁- ▁( return _ type ) instance Method 2 With 2 Parameters