act as 与act for的用法区别是啥

1.act as (临时)担任,充当,起……的作用.如：A trained dog can act as a guide to a blind person.经过训练的狗可以担任盲人的向导.表示担任独一无二的职务,其前通常不用冠词.如：He acted as manager in my absence.我不在时他担任经理.I don’t understand their language; you’ll have to act as interpreter.我不懂他们的语言,你得当翻译了.
2.act for 代理(某人职务),代为(处理某事).如：Please act for me during my absence.我不在时请代理我处理事务.I acted for our captain while he was in hospital