Paddle Mate has some charts, as I mentioned earlier I am using ios-charts by Daniel Cohen. The article that put me onto ios-charts was How to Use iOS Charts API to Create Beautiful Charts in Swift. It is well worth the read if you are looking to add charts to your app.
One thing I have noticed is large spikes in memory when zooming in or panning around the chart. That is something to keep an eye on in your app.
Also great about this library is that it is a port of the Android library MPAndroidChart by Philipp Jahoda, which means you only need to learn one charting library that you can use on two platforms since the code is very similar. Handy if you are supporting both Android and iOS.