NSUserDefaults存储mutable类型实例

一. 下面是调试时2个错误提示, 对两个不可改变的类实例进行修改操作, 问题发生在NSUserDefaults中, 因为NSUserDefaults在序列化存储中, 存储的类型是不可改变的(immutable object), 我们在读取实例时, 把不可改变的NSArray, NSDictionary直接赋给了NSMutableArray, NSMutableDictionary, 对其进行写操作而导致程序异常.

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[__NSCFArray replaceObjectAtIndex:withObject:]: mutating method sent to immutable object'

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[__NSCFDictionary setObject:forKey:]: mutating method sent to immutable object'

引起异常的代码:

[[NSUserDefaults standardUserDefaults] setValue:[[NSMutableArray alloc] init] forKey:key];

我们对NSMutableArray进行序列化存储, 但在NSUserDefaults中,实际存储的类型是NSArray, 是不可变的. 所以读出来的类型是NSArray,无法进行修改, 可以使用下面2种方式重新初始化.

arrayItems = [NSMutableArray arrayWithArray:array];

或

arrayItems = [array mutableCopy];

二. 深一步处理

你的NSMutableArray实例可能还包含有NSMutableDictionary,你也需要递归进行处理.

for (NSDictionary *x in array){NSMutableDictionary * dic = [NSMutableDictionary dictionaryWithDictionary:x];[arrayItems addObject:dic];}