Defer Statement

Defer

Defer statements are used to postpone a statement until the end of the current scope

import basics

func main {
    defer print("One")
    defer print("Two")
    defer print("Three")
    print("I will be printed before anything else")
}

I will be printed before anything else
Three
Two
One

When the end of the scope is reached, or the scope is going to be left, all deferred statements will be executed in the reverse order they were encountered.

Common Uses

The most common use of defer is to free dynamically allocated memory

import basics

func main {
    x_squared_integers *int = new int * 10
    defer delete x_squared_integers
    
    // 0, 1, 4, 9, 16, etc.
    repeat 10, x_squared_integers[idx] = idx * idx
    
    // Print each
    repeat 10, print(x_squared_integers[idx])
}

0
1
4
9
16
25
36
49
64
81