iphone - Programmatically set (System-wide) proxy settings using Pac File?

There’s no way to do this on iOS. In general, iOS app are not allowed to make changes that affect the system as a whole. Most folks who use PAC files are working in the enterprise environment, in which case you’d set this up using a configuration profile installed via MDM. If you’re not working in the enterprise environment, please explain more about your high-level goal.

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Quinn "The Eskimo!"
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

How to do it in enterprise environment?

In an enterprise environment you can use MDM to install a configuration profile to set up the PAC. If you want to initiate that from your app, you can create a web service that allows your app to command the MDM server to do this.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

How about if I just want the PAC apply to my app?

I’m going to respond on your specific thread.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"