objective c - Whats the difference between array[index] and [array objectAtIndex:index]? -

i noticed both array[index] , [array objectatindex:index] work mutable arrays. explain difference between them? in terms of performance, , 1 best practice?

none. that's part of clang extensions objective-c literals, added 2-3 years ago.

also:

array-style subscripting

when subscript operand has integral type, expression rewritten use 1 of 2 different selectors, depending on whether element being read or written. when expression reads element using integral index, in following example:

nsuinteger idx = ...; id value = object[idx]; 

it translated call objectatindexedsubscript:

id value = [object objectatindexedsubscript:idx];  

when expression writes element using integral index:

object[idx] = newvalue; 

it translated call setobject:atindexedsubscript:

[object setobject:newvalue atindexedsubscript:idx]; 

these message sends type-checked , performed explicit message sends. method used objectatindexedsubscript: must declared argument of integral type , return value of objective-c object pointer type. method used setobject:atindexedsubscript: must declared first argument having objective-c pointer type , second argument having integral type.