Software
Xcode
4.0 / 5
Apple's official IDE for iOS, iPadOS, and macOS apps. If you build for the ecosystem, there's no real alternative.
Xcode is the gateway to developing for Apple: editor, simulators, Interface Builder, performance instruments, and signing/distribution, all in one place. For prototyping native interfaces with SwiftUI it's direct and powerful.
It's not free of friction: it eats resources, the big releases are heavy, and sometimes you have to wrestle with code signing and the simulators. But it's the de facto tool, and it gets better release after release.