Swift - Function defer Keyword

Introduction

The defer keyword wraps code to run at a later time.

You can use defer to write the teardown code next to your setup code.

Code you put in a defer block will run when the current flow of execution leaves the current scope.

The current scope includes the current function, loop body, and so on:

Demo

func doSomeWork() { 
    print("Getting started!") 
    defer { //from   w  ww. ja va  2  s  .  c  o  m
        print("All done!") 
    } 
    print("Getting to work!") 
} 
doSomeWork()

Result

The defer block of code is run in between the end of the final print statement, but before the closing brace.

You can do clean up work and return a value.

defer is a resource management and code style technique, not a means of implementing asynchronous code!

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