The LEGO EV3 Mindstorms robot is under the hood a LINUX box. A LINUX box on which you can run an alternative OS to the out-of-the-box-built. An alternative that you can download from https://ev3dev.org website. You have with the alternate a build on which you can choose at least half a dozen real programming languages to code with. You can use any of these with this app to build a controller. A means by which you can use your iOS device to control your LEGO robot. Note you will also need a WIFI chip for your EV3 brick for this to work.
You can find the details of how you do so on the accompanying website. You can read details of what that app should look like in PYTHON on this app website.