Phineas and Ferb is a Disney Channel series that tells of two boys who, during their summer break, decide to create some spectacular or complex invention within the day. However, whatever that creation is, they're usually destroyed or disappear at the end of the day due to the side-plot fight between their secret-agent pet and an evil scientist.
It sounds preposterous and ridiculous, of course (hey, it's a cartoon) but in the past I had the experience of living through a manager who thought exactly this way. On one day, they'd set you off on a task, something that sounds simple while being spoken (it's NEVER written down) but takes days (or weeks, even months) to implement. The following day (or in an otherwise short period of time after) they'd come back to you, looking for their favorite word: "results".
It won't matter if the task they gave you isn't supported in the programming language you're using, or the framework API you're building on. Doesn't matter if the change caused thousands of errors on other parts of the system, and you're stuck deep in the process of fixing those. Doesn't matter if the new task contradicts or conflicts precisely what he asked you to do previously, rendering previous work a waste of time.
If you find yourself serving a manager like this there are two options. First is to suck it up and be the Ferb to his Phineas. These managers have a hard time retaining anybody, and those who suck it up may find it rewarding -- usually in financial terms -- if they stay. Sadly that's almost always at the expense of any life outside of work.
If you don't have the stomach to do that though -- polish that resume now.
A change in direction is unavoidable once in awhile… but doing it often enough usually infuriates those who care enough and want to see real progress.