How to write if/then/elseif/else in Drupal 8 Twig templates

As a quick note Drupal programming note, here’s an example of how to write if/then/elseif/else in Drupal 8 Twig templates:

{% if node.getType == 'photo' %}
{% elseif node.getType in ['book', 'page'] %}
{% else %}
{% endif %}

While I’m in the neighborhood, here are a few more if conditions I’ve written recently:

Scala control structure examples (if/then, match/case, for, while, try/catch)

This post contains a collection of Scala control structures examples. I initially created most of these in the process of writing the Scala Cookbook. Unlike the Cookbook, I don’t describe them much here, I just show the examples, mostly as a reference for myself (and anyone else that can benefit from them).

if/then control structures:

Here are some examples of the Scala if/then control structure:

Scala if then else syntax (and returning a value from an if statement)

Scala FAQ: Can you share some examples of the Scala if/then/else syntax? Also, can you show a function that returns a value from an if/then/else statement?

In its most basic use, the Scala if/then/else syntax is very similar to Java:

Perl next operator - for loop and if statement examples

Perl next loop FAQ: Can you demonstrate how to use the Perl next operator in a for loop?

Problem: You're writing code for a Perl loop, and you need to write some logic to skip over the current element in the loop, and move on to the next loop element.

The Perl unless operator

Perl unless FAQ: Can you share some examples of the Perl unless operator?

Perl has a cool keyword named "unless" that can make your code easier to read and write from time to time. The Perl unless operator is similar to the Perl "if" keyword ... but a little different.

A Perl unless/else example

Here's a quick example (inspired by one of the Star Trek movies) that shows how to use the Perl unless syntax. Hopefully it's fairly easy to read, in part due to the unless operator:

How to use the Perl ternary operator

In most languages there is an operator named the "ternary" operator that lets you write concise if/then statements. This makes for less verbose, which is generally a good thing. Perl also has a ternary operator, and I'll demonstrate it here.

General syntax of the ternary operator

The general syntax for Perl's ternary operator looks like this:

test-expression ? if-true-expression : if-false-expression

Let's take a look at a brief example to demonstrate this.

Perl if, else, elsif ("else if") syntax

Summary: This tutorial shows a collection of Perl if, else, and else if examples.

Here are some examples of the Perl if/else syntax, including the “else if” syntax, which is really elsif. (I wrote this because after working with many different languages I can never remember the “else if” syntax for most languages, and elsif is pretty rare.)

The Perl if/else syntax

The Perl if/else syntax is standard, I don’t have any problems here:

Perl ‘equals’ FAQ: What is true and false in Perl?

Perl true/false FAQ: What is true in Perl? What is false in Perl?

The Perl programming language is a little unusual in not having true and false boolean operators. Because of this, I can never seem to remember what equates to true and false in Perl, so I decided to create this page.

What is true/false in Perl

In short, the following elements evalue to false in Perl:

Perl comparison operators

Perl equality FAQ: Can you share a list of the Perl equality operators?

Sure. Here's a convenient list of the Perl comparison operators (also known as Perl equality operators, equal, or not equal operators).

The Perl comparison operators are different for numeric and string comparison tests, as you can see in the following table: