I have a Swift file in my app that has about 4,500 lines of code, and will likely need to grow to at least 7,000. The amount, or some sections of this amount of lines, is causing my ability to type in this particular .swift file to lag. I've tried to clean it up a bit, but much of it is design, front-end code that seems hard to put into other files...
Any advice on how to speed up my ability to type in this .swift file? It is very annoying, and my other, smaller .swift files in the project do not have this problem.
As other comments have said, you need to refactor your large file into smaller components. This will not only improve compile times, but will also make your code more manageable.
Here are some really great talks about refactoring code specifically for iOS:
WWDC 2014: Advanced iOS Application Architecture and Patterns