iphone - Cocoa consistency -


if can write:

test_string = [[nsstring alloc] init]; , test_date = [[nsdate alloc] init];

why, if reasons of consistency, can't write:

test_integer = [[nsinteger alloc] init]; or test_decimal = [[nsdecimal alloc] init];

and how set them up?

your first 2 examples real objects, must instantiated alloc/init (or shorthand form, new.

an nsinteger typedef int or long, depending on platform, is, name either int or long. both so-called primitive types. they're not real objects, simpler. don't have methods, ivars, etc. - in fact, numbers, while object representing number (for example [nsnumber numberwithint:1]) more.

primitive types used when speed , memory efficiency important, , integers used considerations important here. way, smalltalk (the language inspired objective-c's syntax , object model) did not have primitive types. integers, boolean values objects. more consistent (and more powerful in regards), 1 of factors made smalltalk quite slow in seventies , eighties.

nsdecimal not object, struct. struct list of named primitive values. other often-used structs in objective-c might more obvious cgpoint (a struct containing 2 floats, x , y), cgsize (again struct containing 2 floats, time called width , height), cgrect (a struct containing cgpoint struct named origin, , cgsize struct named size).


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