平成30/ 2018-12-19 21:48
Xcode/ Main.storyboad/ メモリ消費し、Swap 起きる。表示されない。/ storyboad のソースに問題があった。<toolbar translatesAutoresizingMaskIntoConstraints="NO"> を"YES"にしたら直った。

この人のおかげ。Thanks.

Xcode 9.0.1 Interface Builder 100% CPU opening iOS Storyboard
https://stackoverflow.com/questions/46922321/xcode-9-0-1-interface-builder-100-cpu-opening-ios-storyboard

I received a response from my bug report with a suggested workaround. The suggestion was to edit the storyboard text and change the value for the translatesAutoresizingMaskIntoConstraints attribute from NO to YES in the applicable toolbar tags in the storyboard.

From:

<toolbar opaque="NO" clearsContextBeforeDrawing="NO" contentMode="scaleToFill"
fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="KCx-9L-amg">

To:

<toolbar opaque="NO" clearsContextBeforeDrawing="NO" contentMode="scaleToFill"
fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="YES" id="KCx-9L-amg">
I have two storyboard files in my project and this does solve the problem with both of them.