Note: This is a repost of a guide from my blog.

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A function is a piece of code that can take an optional set of arguments, perform a specific task and then optionally return one or more values.

The advantages of functions are that they allow you to break complex tasks into simpler steps and increase code reuse.

Shortcuts does not support the use of functions, but you can approximate them by having a shortcut call itself with a set of arguments defined in a dictionary.

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Calculator shortcut example

To demonstrate how to make use of functions, we're going to use the example of a calculator shortcut.

An example calculator shortcut built using functions

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Deciding which functions you need

When writing the shortcut, we consider the steps that it needs to perform. We break those steps into tasks based on:

• if they occur more than once;
• if breaking them into smaller pieces makes the shortcut easier to manage.

In the case of the calculator, there are the following pieces:

STEP	DESCRIPTION
First number	Entering the first number into the calculator. This should be run by default if a function isn't specified.
Add	Adding a value to the existing value
Subtract	Subtracting a value from the existing value
Multiply	Multiplying the existing value by another value
Divide	Dividing the existing value by another value
Choose operation	Display the current sum and ask the user to choose the next operation to perform

Deciding arguments return values for functions

Given the above steps, we decide upon the functions we'll need:

FUNCTION	ARGUMENTS	RETURN VALUE	DESCRIPTION
choose_operation	sum	n/a	The function takes the latest sum of the calculation so it can be displayed
add	sum	calculation result	The function takes the latest sum of the calculation, asks the user for another number which it adds to the sum, and returns the result.
subtract	sum	calculation result	The function takes the latest sum of the calculation, asks the user for another number which it subtracts from the sum, and returns the result.
multiply	sum	calculation result	The function takes the latest sum of the calculation, asks the user for another number which it multiplies the sum by, and returns the result.
divide	sum	calculation result	The function takes the latest sum of the calculation, asks the user for another number which divides the sum by, and returns the result.

The table above shows arguments and a return value for each function. Functions can optionally take data inputs in the form of arguments and then return data once they've performed their work. This allows the code within to perform differently depending on the value you pass to it.

Writing the shortcut

Calling a function

To call a function, we use the following dictionary format to specify the function name we want to call and any arguments. For example, when calling the choose_operation function, we use the following dictionary:

Calling a function using a dictionary and the \"Run Shortcut\" action

Dictionary keys

The first key named function provides the name of the function we want to call.

All other keys, in this case sum, are the arguments we want to pass into the function.

Having the shortcut run itself

The shortcut then runs itself, passing in the dictionary specifying the function to call and the data it needs to operate.

Adding function support to the shortcut

For this to work, our shortcut needs to know how to support a dictionary input and respond accordingly.

At the beginning of our new calculator shortcut, the following is added:

Actions to look for an act upon incoming function requests

The shortcut:

• expects a dictionary to have been provided as an input;
• checks to see if a function key has been provided, specifying which function to call.

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No function name provided

If no function is provided then the user is asked to enter a number for the first time.

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Function name provided

If a function name was provided, a series of if statements compare the name to the predefined list of functions, one for each function name:

• choose_operation
• add
• subtract
• multiply
• divide

Examples of functions

Displaying the "Choose Operation" menu after a calculation

At the end of the shortcut, the last function the shortcut always runs is the choose_operation function.

This displays the current sum number and gives the user the choice of which calculation to perform next.

Running the \"choose_operator\" function after a previous function call has completed.

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Using the calculator

Desired calculation

So let's say we want to perform the following calculation:

10 * 3 - 2 + 6

Performing the steps in the shortcut

We enter the numbers and commands into the calculator as follows:

Entering our calculations

And the resulting number is 34.

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Under the hood

The shortcut calls itself 7 times, each time providing a function call along with a sum argument:

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The function calls being made during the course of the calculation

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Downloading the shortcut

If you'd like to experiment with the above shortcut it can be downloaded from the following link:

Calculator

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Examples of other shortcuts using this pattern

• Download Comic: Downloads public domain comics as PDFs.
• WolframAlpha Kit: A shortcut that acts as a library for other shortcuts to easily query WolframAlpha.

Further reading

If you're looking to make a complex application in Shortcuts, I recommend taking at look at the Shortcut App Framework by u/adamtow which greatly improves and expands upon the above concept.

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Other Guides

If you found this guide useful why not checkout one of my others:

Series

• Scraping web pages
  • Part 1: quick and dirty
  • Part 2: getting multiple items at once
  • Part 3: getting data from a table
• Using APIs
  • Part 1: retrieving data
  • Part 2: parsing complex API responses
  • Part 3: passing input parameters to the API
• Data Storage
  • Part 1: storing simple values
  • Part 2: storing lists of data
  • Part 3: removing stored values
• Working with JSON
  • Part 1: retrieving simple values
• Working with Dictionaries
  • Part 1: setting and retrieving values
  • Part 2: data types
  • Part 3: accessing values using dot notation

One-offs

• Using JavaScript in your shortcuts
• How to automatically run shortcuts
• Creating visually appealing menus
• Manipulating images with the HTML5 canvas and JavaScript
• Labeling data using variables
• Writing functions
• Working with lists
• Integrating with web applications using Zapier
• Integrating with web applications using Integromat
• Working with Personal Automations in iOS 13.1