Issue with animating constraints about masonry HOT 6 CLOSED

In RootViewController if you change [_listController.view layoutIfNeeded]; to [self.view layoutIfNeeded];, the view will animate as you desire (though this is sort of a hacky workaround). Best of luck to you.

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This doesn't address the actual issue. The recommended solution above is just a hacky workaround. What I'm really trying to figure out is how to make it work properly, and more importantly, why it's behaving like this in the first place.

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sometimes Auto Layout does not recognise it needs updating so you can explicitly tell it.

[self.listController.view setNeedsLayout];    
[UIView animateWithDuration:0.25 animations:^{
    [self.listController.view layoutIfNeeded];
}];

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Beast. How did you figure this out?

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This is my Guesstimation of the situation.

Because you are creating layout constraints between self.listController.view and self.view these constraints have to be added to the closest common superview of self.listController.view and self.view which in this case is self.view (Masonry does this for you). Therefore self.listLeftConstraint only updates after self.view has finished re-laying out which would happen on the next runloop and not within your animation block as self.listController.view doesn't think it needs laying out yet. Adding [self.listController.view setNeedsLayout] forces the layout to happen within your animation block. Hope that helps and thanks for trying out Masonry.
Also for a good auto layout read checkout http://www.objc.io/issue-3/advanced-auto-layout-toolbox.html

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adding subviews in addSampleView has the same effect as changes to the view hierarchy ie addSubview, removeFromSuperview etc will trigger setNeedsLayout

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