iOS – EncodeWithCoder – 编码Nil

我有一个对象,其属性可能为零.我应该如何在encodeWithCoder(和decodeWithCoder)中实现它？

- (void)encodeWithCoder:(NSCoder *)aCoder
{ 
    [aCoder encodeObject:_duration forKey:kDuration]; //_duration Could be nil
}

解决方法

- (void)encodeWithCoder:(NSCoder *)aCoder
{ 
    if (_duration) {
        [aCoder encodeObject:_duration forKey:kDuration]; //_duration Could be nil
    }
}

(如果密钥不存在,您的对象将在解码时为零.)