In Swift, the “defer” keyword is used to specify the code to run at the end of a code block or function. No matter how complex this code block or function is, the code specified with the defer keyword is automatically executed to ensure that the block or function is complete.
The defer keyword is particularly useful for releasing resources, closing file operations, or performing other cleanup operations. Using Defer saves programmers from manually freeing up resources and making the code more readable and maintainable.
Example code block using Defer:
func processFile(filename: String) throws {
let file = openFile(filename)
defer {
closeFile(file)
}
while let line = try file.readLine() {
// process the file
}
// file is automatically closed here
}
In the example above, the “openFile” function opens the file and the “closeFile” function closes the file. The “defer” keyword automatically executes the “closeFile” function to ensure that the file is finished using.
