翻译By the time he comes,I'll have left.( By the time he came,

By the time he comes, I'll have left. 他来之前,我就将已经走了.（这里是将来完成时,表示在将来某一时间之前已完成的动作,并往往对将来某一时间产生影响.）
( By the time he came, I had left. )意思差不多,就是他来之前,我已经走了.表示过去发生情况.
by the time经常跟完成时