How to manually deprecate members in iOS Swift?

In iOS Swift, you can manually deprecate members (properties, methods, and other members) by using the @available attribute with the deprecated argument.

@available

The @available attribute in Swift is used to specify the availability of a particular piece of code. It can be used to mark a class, function, method, property, or enumeration as available or unavailable for a particular platform, version, or architecture.

Here's an example syntax of the @available attribute

@available(platform version, *)

The platform argument specifies the platform on which the code is available (e.g. iOS, macOS, watchOS, tvOS). The version argument specifies the version of the platform on which the code is available, or a range of versions if needed (e.g. "13.0", ">=14.0"). The * argument specifies that the code is available on all platforms.

@available(iOS 14.0, *)
class MyClass {
   // class definition here
}

In our previous example, we used the @available attribute with the deprecated argument to mark a method as deprecated. The deprecated argument specifies the version at which the code was deprecated, and can include a message explaining why it was deprecated.

Deprecating a Method

To deprecate a method, you can add the @available attribute with the deprecated argument to the method's declaration. You can also provide a message to explain why the method was discontinued and what the developer should use instead.

Deprecating a Class

To deprecate a class, you can add the @available attribute with the deprecated argument to the class's declaration. You can also provide a message to explain why the class was deprecated and what the developer should use instead.

Deprecating a Property

To deprecate a property, you can add the @available attribute with the deprecated argument to the property's declaration. You can also provide a message to explain why the property was no longer valid and what the developer should use instead.

Using Deprecation Attributes

When you use the @available attribute to deprecate a member, you can provide several arguments −

• deprecated − this argument marks the member as deprecated.

• message − this argument provides a message to explain why the member was deprecated and what the developer should use instead.

• renamed − this argument indicates that the member has been renamed. You can provide the new name as an argument value.

• unavailable − this argument indicates that the member is no longer available and should not be used.

Example

import Foundation
class Person {
    
   @available(*, deprecated, message: "Use fullName instead.")
   var name = ""
   var age = 0
   var address = ""
   var fullName = ""
    
   @available(*, deprecated, message: "Use displayFullInfo() instead.")
   func displayInfo() {
      print("Person name: \(name)")
   }
    
   func displayFullInfo() {
      print("Person name: \(fullName)")
   }
}
// Create an instance of the Person class
let alex = Person()
alex.name = "Alex"
alex.fullName = "Alex Murphy"
alex.displayInfo()
alex.displayFullInfo()

We then create an instance of Person called alex, and call displayInfo(). Since displayInfo() is marked as deprecated, Xcode will show a warning in the console with the deprecation message −

Output

'displayInfo()' was deprecated: Use displayFullInfo() instead.
Person name: Alex
Person name: Alex Murphy

Key points to keep in mind when manually deprecating members in iOS Swift

• To designate a member as obsolete, use the @available property along with the deprecated argument.

• Explain why the member was retired and what the coder should use in its place in the message argument.

• Additionally, you can specify that a member has been renamed using the renamed argument and supply the updated name as an argument value.

• A class, function, or object can be designated as deprecated using the @available attribute.

• When the deprecated component is used in the code, Xcode displays deprecation alerts.

• Use deprecation to let other programmers know about changes to your code and nudge them towards using the upgraded and improved version.

Conclusion

In conclusion, Swift's @available attribute is a powerful utility that lets writers define which systems, versions, and architectures their code is compatible with. Developers can designate a class, function, method, or variable as obsolete and add a message explaining why it was discontinued. They can also explain what the developer should use in its place by using the @available trait with the deprecated argument.

This method of using deprecation is crucial for keeping the code up-to-date over time. It allows developers to keep their code current and compliant with best practices. Developers can help other developers understand the changes in their code and in making the required updates to their own code. This is done by providing them with concise and helpful deprecation messages.