Swift 4中如何调用独立函数文件？Matlab用户技术求助

Hey there! I totally get where you're coming from—switching from MATLAB's dead-simple standalone .m function setup to Swift's module-based system can feel a bit confusing at first. Let's walk through exactly how to fix this so you can call your fibonacci(until:) function from other files or a Playground without copying code.

First: Understand Swift's Module System #

Unlike MATLAB, where any .m file in the same directory is automatically accessible, Swift organizes code into modules. A module is a collection of files that work together, and code within the same module can access each other without imports (as long as access levels allow). You can't directly "import" a single .swift file—you import entire modules instead.

Solution 1: Calling the Function in an Xcode Project #

If you're working in a standard Xcode project, follow these steps:

1. Ensure your function file is in the correct target

   • Open your project settings, go to the Build Phases tab, and check the Compile Sources section.
   • Make sure Fibonacci.swift is listed here. If not, drag the file from your project navigator into this list.
   • Now, any other file in the same target can call fibonacci(until:) directly—no import needed! For example:

     // In another file like ViewController.swift
     let fibSequence = fibonacci(until: 20)
     print(fibSequence) // Output: [0, 1, 1, 2, 3, 5, 8, 13]
     

2. If you want to reuse the function across multiple projects

   • Create a Framework project (File > New > Project > Framework).
   • Add Fibonacci.swift to the framework, and update the function's access level to public (so it's visible outside the framework):

     public func fibonacci(until limit: Int) -> [Int] {
         var sequence = [0, 1]
         while let last = sequence.last, 
               let secondLast = sequence.dropLast().last, 
               last + secondLast < limit {
             sequence.append(last + secondLast)
         }
         return sequence
     }
     

   • Build the framework, then add it as a dependency to your main project.
   • Import the framework in your main project's files and call the function:

     import MyFibonacciFramework
     let fibSequence = fibonacci(until: 30)
     

Solution 2: Calling the Function in a Playground #

Playgrounds work a bit differently—here's how to make your standalone function accessible:

Option A: Project-linked Playground #

• Add the Playground directly to your Xcode project (File > New > Playground, then save it inside your project directory).
• Ensure the Playground is assigned to the same target as Fibonacci.swift (check the Playground's inspector panel on the right).
• You can now call fibonacci(until:) directly, no import required.

Option B: Independent Playground #

• Create a new standalone Playground.
• In the Playground's navigator, right-click the Playground file and select New Folder. Name this folder Sources.
• Drag your Fibonacci.swift file into the Sources folder (this folder acts as a mini-module for the Playground).
• Update the function to have public access level (as shown in the framework example above).
• Import the auto-generated module (named after your Playground) at the top of your Playground, then call the function:

  import MyFibonacciPlayground
  let fibSequence = fibonacci(until: 15)
  print(fibSequence)
  

Why Your Initial Attempt Failed #

• You can't import a single .swift file in Swift—imports are for entire modules.
• If the function wasn't marked public, it had the default internal access level, which means it's only visible within its own module.

内容的提问来源于stack exchange，提问作者Harry B