ios - Can't modify array stored in NSUserDefaults -

in class firstviewcontroller, add array key renteditems nsuserdefaults in following lines:

let itemarray = [item]() let prefs:nsuserdefaults = nsuserdefaults.standarduserdefaults() prefs.setobject(itemarray, forkey: "renteditems") 

then, in class secondviewcontroller, try

var item: item? var prefs:nsuserdefaults = nsuserdefaults.standarduserdefaults()      func confirmpressed() {     prefs.arrayforkey("renteditems")?.append(item) } 

this gives following error: cannot use mutating member on immutable value: function call returns immutable value. saw solution in here gave me idea of problem, nsuserdefaults being default ios class, can't use same solution there. ideas?

you can't directly modify array defaults. instead make copy, , modify that. can save array defaults afterwards. try this:

var array = prefs.arrayforkey("renteditems")?.mutablecopy array.append(item)