Section 1.1: Public Access

Public access is the most open level, enabling any code to interact with the entity. To designate an entity as public, simply utilize the public keyword. For instance:

public class SomeClass {}

public struct SomeStruct {}

public enum SomeEnum {}

Any code within your application and external frameworks or libraries can access a public entity.

Section 1.2: Internal Access

Internal access is slightly more restrictive, allowing only code within the same module to access the entity. To mark an entity as internal, use the internal keyword, as shown below:

internal class SomeClass {}

internal struct SomeStruct {}

internal enum SomeEnum {}

Entities designated as internal can be accessed by any code within the same module, which is defined as a single target in Xcode (such as an app or framework).

Section 1.3: File-Private Access

File-private access limits access to the enclosing file. To specify this access level, use the fileprivate keyword:

fileprivate class SomeClass {}

fileprivate struct SomeStruct {}

fileprivate enum SomeEnum {}

Only code within the same file can access entities marked as file-private.

Section 1.4: Private Access

Private access is the most restrictive, allowing only the enclosing declaration to access the entity. Use the private keyword to mark an entity as private:

private class SomeClass {}

private struct SomeStruct {}

private enum SomeEnum {}

A private entity can only be accessed by code within the same declaration, which adds a layer of encapsulation.

Section 1.5: Open Access

In addition to the four access levels mentioned, Swift also includes a fifth level: open. Open access resembles public access but allows entities to be subclassed and overridden in other modules. To declare an entity as open, use the open keyword:

open class SomeClass {}

open struct SomeStruct {}

open enum SomeEnum {}

Entities marked as open can be accessed and subclassed by code in other modules.

Now that you understand the five access levels in Swift, you may wonder how to choose the appropriate one for your code. As a general rule, opt for the most restrictive level that satisfies your requirements.

If you are developing a framework or library for external use, consider using open or public access to enable other developers to subclass and extend your code. Conversely, if you are part of a team working on an app, internal access is advisable, as it provides access to your colleagues while limiting exposure to external developers. For personal projects, file-private or private access is suitable, as it restricts other developers from utilizing your code without affecting your app's functionality.

Summary

Understanding access control is crucial in Swift development. By applying the most restrictive access level necessary, you enhance the robustness and maintainability of your code. If you're just beginning with Swift, mastering access control is a fundamental skill to develop.

The first video, "Swift Access Control Explained," provides an insightful overview of access control in Swift, illustrating its importance and practical applications.

In the second video, "How to use Access Control (Private vs Public) | Swift Basics #12," viewers will learn about the distinctions between different access levels, enhancing their understanding of Swift's access control mechanisms.

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