What does a module mean in swift?
swift
Solution
A module is a single unit of code distribution—a framework or application that is built and shipped as a single unit and that can be imported by another module with Swift’s import keyword.
Each build target (such as an app bundle or framework) in Xcode is treated as a separate module in Swift. If you group together aspects of your app’s code as a stand-alone framework—perhaps to encapsulate and reuse that code across multiple applications—then everything you define within that framework will be part of a separate module when it’s imported and used within an app, or when it’s used within another framework.
As the docs indicate, the module is an application or a framework (library). If you create a project with classes `A` and `B`, they are part of the same module. Any other class in the same project can inherit from those classes. If you however import that project to another project, classes from that another project won't be able to subclass `A` nor `B`. For that you would have to add `open` indicator before their declarations.
Basically, if you work on a single app then you are working in one single module and unless declared as `private` or `fileprivate`, the classes can subclass each other.
EDIT
Let us have following class in module (project) Module1:
class A {
}
Since this class is not `open`, it can be subclassed only within the same module. That means that following class:
class B: A {
}
Can be written only in the same project, in Module1.
If you add Module1 as a dependency to project Module2, and try to do this:
import Module1
class C: A {
}
It will not compile. That's because class `A` is not `open` (in other words it has access `public` or less) and it does not belong to the same module as `C`. `A` belongs to Module1, `C` belongs to Module2.
Note
`import` keyword imports a dependency module to your current module. If you write `import UIKit` in your project, you are telling the compiler that you want to use module `UIKit` in your module. `import` does not define current module. Current module is the current project.
Adding `import UIKit` at the beginning of the file does not change nor define to which module the file belongs. It just tells the compiler that in that file you want to use code from `UIKit` module.
Problem
For example, I have two files called `file1.swift` and `file2.swift`. `file1.swift`: ``` import UIKit class A: B { } ``` `file2.swift`: ``` import UIKit class C: A{ } ``` I am reading that public class can not subclassed outside of module. Here I have subclass C. I am trying to understand what does module mean here. I imported to same module UIKit for both file. So the both files are of same module? So that I can subclassed. Or both files have different module even I import the same UIKit? Can anybody explain what is module? Source: Classes with public access, or any more restrictive access level, can be subclassed only within the module where they’re defined. Class members with public access, or any more restrictive access level, can be overridden by subclasses only within the module where they’re defined.