Why do custom views not display？

[qianlipeng]

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[Fando]

Hey, this is why your custom view is not showing up. mwfire/PopupDialogCustomExample#2 (comment)

I was struggling with the same issue until I found this comment. Specifically the point: Make sure to have a seamless chain of constraints from top to bottom.

Here's a list of reasons for why your custom view might not be showing

1. You don't have any elements inside your view so the height ends up being 0, or
2. If you are testing an empty view, you should set a specific height constraint, or
3. If you have elements in your view, Make sure to have a seamless chain of constraints from top to bottom. This way, the dialog height will adapt to the height of the elements inside the view.

I had constraints on all my views, but they were not a seamless chain from top to bottom. One missing constraint was breaking the chain, and preventing the view height from being determined by the PopupDialog. This was causing the view height to be calculated as zero.

Also, do not confuse, "Unable to simultaneously satisfy constraints", with "a non-seamless constraint chain", they are not the same. In my case, all constraints were satisfied and none were conflicting, but there was no seamless chain from top to bottom.

I hope this saves someone time! I'm an iOS noob, learning the ropes.