ios - Why `NSUserDefaults` not allowed to store objects of Custom Classes? -

i've seen nsuserdefaults not allow objects other array, dictionary, string, nsdata, nsnumber, bool, nsdate. but

• why not allowed store other objects?
• what if need store properties single object? if using dictionary, i've write keys somewhere i've used store value. so, other alternatives.
• what problems arise if apple allows other objects store.
• what if use coredata instead nsuserdefaults. know nsuserdefaults globally available.
• what best way make value available globally after relaunched app if terminated?

as suggested @hoa, forgot mention nscoding option also

• what if have many properties in custom class, need encode , decode of them using nscoding methods?

you can save object plist file long compliant nscoding protocol.

you can use code similar this:

+(id) readobjectfromfile:(nsstring*) sfilename {     return [nskeyedunarchiver unarchiveobjectwithfile:sfilename]; }   +(bool) saveobject:(id <nscoding>) anobject tofile:(nsstring*) sfilename {     nsdata * data = [nskeyedarchiver archiveddatawithrootobject:anobject];     nserror * error;     [data writetofile:sfilename options:nsdatawritingatomic error:&error];     if (error)         {             nslog(@"save cats data error: %@", error.description);             return no;         }     return yes; } 

swift version:

func readobjectfromfile(sfilename: string) -> anyobject {    return nskeyedunarchiver.unarchiveobjectwithfile(sfilename) }  func saveobject(anobject: anyobject, tofile sfilename: string) -> bool {     var data: nsdata = nskeyedarchiver.archiveddatawithrootobject(anobject)     var error: nserror     data.writetofile(sfilename, options: nsdatawritingatomic, error: error)     if error != nil {         print("save cats data error: \(error.description)")         return false     }     return true } 

to learn more nscoding protocol can read: https://developer.apple.com/library/mac/documentation/cocoa/reference/foundation/protocols/nscoding_protocol/