From the official documentation:
If you want to get advanced, you can also open up the project file for a specific platform by opening the required XCode or Android Eclipse project in platforms/PLATFORM inside the root of your project. Then, you can build and test from inside the platform-specific IDE. Note: if you go this route, I recommend still working inside of the root www folder, and when you've made changes to this folder, run the command:
$ cordova prepare ioswhich will update the iOS specific project with the code from the
wwwfolder. Note: this will overwrite any changes you've made to the
platforms/ios/wwwand other platform-specific folders.
So, to summarize this part - if you're using XCode to test and run your code, after you change some part of the code you just have to run
ionic prepare to update the iOS project which then again you continue to use in XCode.
ionic build command actually prepares the final (for example in Android it's the .apk file) file which then could be copied to your device and test by running it manually on the device (or by using the
ionic emulate command to test it on the emulator).