MPMoviePlayerController "thumbnailImageAtTime:timeOption:" selector does not exist

This code

MPMoviePlayerViewController* mp = [[MPMoviePlayerViewController alloc] initWithContentURL:url];

    int i=0;
    unsigned int mc = 0;
    Method * mlist = class_copyMethodList(object_getClass([mp moviePlayer]), &mc);
    NSLog(@"%d methods", mc);
    for(i=0;i<mc;i++)
        NSLog(@"Method no #%d: %s", i, sel_getName(method_getName(mlist[i])));
    /* note ml开发者_如何学JAVAist needs to be freed */

    if  ([[mp moviePlayer] respondsToSelector:@selector(thumbnailImageAtTime:timeOption:)])
    {
        image = [[mp moviePlayer] thumbnailImageAtTime:(NSTimeInterval)2.0 timeOption: MPMovieTimeOptionNearestKeyFrame];
    }
    [mp release];

print this Log

45 methods

Method no #0: pause

Method no #1: stop

Method no #2: initialPlaybackTime

Method no #3: setInitialPlaybackTime:

Method no #4: scalingMode

Method no #5: setScalingMode:

Method no #6: contentURL

Method no #7: initWithContentURL:

Method no #8: movieSourceType

Method no #9: setMovieSourceType:

Method no #10: movieMediaTypes

Method no #11: prepareToPlay

Method no #12: isPreparedToPlay

Method no #13: isFullscreen

Method no #14: setUseApplicationAudioSession:

Method no #15: shouldAutoplay

Method no #16: setShouldAutoplay:

Method no #17: controlStyle

Method no #18: setControlStyle:

Method no #19: setContentURL:

Method no #20: setFullscreen:animated:

Method no #21: useApplicationAudioSession

Method no #22: playableDuration

Method no #23: setEndPlaybackTime:

Method no #24: endPlaybackTime

Method no #25: loadState

Method no #26: dealloc

Method no #27: view

Method no #28: init

Method no #29: forwardInvocation:

Method no #30: backgroundView

Method no #31: methodSignatureForSelector:

Method no #32: duration

Method no #33: play

Method no #34: setRepeatMode:

Method no #35: playbackState

Method no #36: setFullscreen:

Method no #37: naturalSize

Method no #38: skipToBeginning

Method no #39: repeatMode

Method no #40: beginSeekingBackward

Method no #41: beginSeekingForward

Method no #42: endSeeking

Method no #43: skipToNextItem

Method no #44: skipToPreviousItem

There is no any of thumbnail selectors.

Who know reason of this strange behavior?

Objective-C has multiple-level dispatch, so it's possible that the method you're interested in is implemented lazily or by forwarding. To see if it's lazily resolved, just move your loop to after you call the method.

While the above is all true, the method you're looking for is on MPMoviePlayerController, not MPMoviePlayerViewController.