To align one button to another in storyboard do this. Drag out your second button and center it by control dragging out and selecting ‘Center Horizontal’.

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Then, to make your second button trail the first, control drag second to first and select ‘Vertical Spacing’.

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You can then double click on the constraint to set whatever spacing you like.

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To test your layout select ‘Update Frames’ from the triangle located near the bottom of the storyboard frame.

 

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And to see all your constraints,  select this well hidden slider, Hide Document Outline, near the bottom left of the storyboard screen.

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And you should see a frame slide out showing you all the constraints for your current project.

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