Is the class open public or private?

The open class is public. The difference from just public is that open classes and class members declared as open can be inherited and overridden outside the module in which they are defined. public classes are accessible for use outside the module but cannot be inherited or overridden unless marked as open.

Access levels in Swift:

• open: The highest access level. Available from any module and can be inherited and overridden.
• public: Available from any module but cannot be inherited or overridden outside the module.
• internal: The default access level. Available only within the same module.
• fileprivate: Available only within the file where it is defined.
• private: The lowest access level. Available only within the declaration where it is defined.

Example:

// Declaration of an open class in ModulesA.swift
open class OpenClass {
    open func openMethod() {
        print("This is an open method.")
    }
}

// Usage in ModulesB.swift (another module)
import ModulesA

class MyClass: OpenClass { // Inheritance is allowed
    override func openMethod() { // Overriding is allowed
        super.openMethod()
        print("This is an overridden open method.")
    }
}

// Declaration of a public class in ModulesA.swift
public class PublicClass {
    public func publicMethod() {
        print("This is a public method.")
    }
}

// Usage in ModulesB.swift (another module)
import ModulesA

let instance = PublicClass()
instance.publicMethod() // Usage is allowed

// class MyOtherClass: PublicClass { // ERROR: Public class cannot be subclassed outside of its module
//     override func publicMethod() { // ERROR: Public method cannot be overridden outside of its module
//         super.publicMethod()
//     }
// }