Objective-c pointers magic. Type protection -

i have dictionary. extract 1 of values follows:

nsstring *magicvalue= [filterdict valueforkey:[filterdict allkeys][0]]; [someclass foo: magicvalue]; 

and foo is:

- (void)foo:(nsstring*)magicvalue {     nslog("magicvalue string:%@",[magic iskindofclass:[nsstring class]] ? @"yes" : @"no");     nslog("magicvalue number:%@",[magic iskindofclass:[nsnumber class]] ? @"yes" : @"no"); } 

if dictionary value number magicvalue nsnumber. defined string pointer pointing nsnumber. log return yes number check.

i never added protection such methods, check class "magicvalue" is. assumed when define method string parameter string.

should start accounting such behavior , add checks, or fault of guy assigned dictionary value magic in such way , used method. need best practices advice , how handle this.

this question have been answered didn't know how search it.

short answer: no, not check that, if there no special reason.

long answer:

you have differentiate between 2 cases:

a. using id

you have variable or return vale of type id. in example -valueforkey:. reason typing keep method generic. theoretically possible, in practice type mismatch in such situation rare , detected fast in development. different motivation asked audience (>200) in public talk, how many times had such typing error in production. listeners, of apps in of app's versions there 1(in words: one!) case. forget risk. anxiety of developers using statically typing languages (java, c++, swift).

b. wrong assignment

if not have id type, still possible such tricks. (and want that. strength of dynamic typing.) there 2 subcategories:

you can implicitly:

nsstring *string = [nsnumber numberwithint:1]; 

the compiler warn that. fine, because developer see mistake. not have protect him or code.

one can explicitly:

nsstring *string = (nsstring*)[nsnumber numberwithint:1]; 

in such case, code can break. did explicitly. if wrong, developer had criminal energy , not have protect him himself.