在NSUserDefaults中存储自定义类型的数据

将自定义的类的数据以数组的形式直接存储到NSUserDefaults中会报错，需要进行转换，且需要将该类实现NSCoding协议。

e.g.

存储过程

NSMutableArray *archiveArr = [NSMutableArray arrayWithCapacity:self.STNArrayList.count];
for (STNArrayList *singleList in self.STNArrayList) {
         NSData *listEncodedObject = [NSKeyedArchiver archivedDataWithRootObject:singleList];
         [archiveArr addObject:listEncodedObject];
          
       }
//可以将archiveArr存入NSUserDefaults中了

读取过程

NSArray *localSavedArr = ;//从NSUserDefaults中读取本地存储的数据
        NSMutableArray *mutableArr = [NSMutableArray arrayWithCapacity:localSavedArr.count];
        for (NSData *data in localSavedArr) {
            STNArrayList *singleList = [NSKeyedUnarchiver unarchiveObjectWithData:data];
            [mutableArr addObject:singleList];
        }

// 现在可以访问mutableArr来获得STNArrayList的值

在STNArrayList类中实现NSCoding协议

- (id)initWithCoder:(NSCoder *)aDecoder
{
    if (self == [super init]) {
        _title = [aDecoder decodeObjectForKey:JSON_KEY];
    }
    return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:_title forKey:JSON_KEY];
}