Code Generation Script for iOS

In this article, I will show you an example of how can you speedup development with code generation scripting.

How can you speed up development with scripted code generation?

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For code generation, I usually use Python or Ruby as these languages have a lot of libs for the generation of boilerplate code. And also these languages are first-class citizenship on macOS.

Real-life example: I had a lot of color themes in an application and a lot of colors, my designer changed colors once every month and added a new theme once a year.

Information was provided in JSON format:

I had theme name and color type name with HEX code of color for light and dark modes.

So how should I convert this into the code?

In common situation you can transform hex into UIColor like that:

But it is really uncomfortable to use colors in this way. I prefer color literal because can see the color:

Yeah, it is much better. Let’s do it this way.

First of all, we should create a swift file where our colors will be — “AppColors.generated.swift”.

After that, as we are using Ruby we should prepare a project for using Ruby.

• Make sure Ruby and Gem are installed;
• Call the bundle install command in the project’s iOS root folder — it will install the required gems;
• Liquid is one of the required gems — we will use it for creating templates.

Also, we should have raw resources for colors — JSON with colors. Let’s name it “ios_colors.json”.

The liquid is very useful for preparing templates. Example of our template “ColorsTemplate.liquid”:

Now the most interesting process — writing script. I will just leave code on Ruby:

Ok, usually I save all scripts in the root directory as it is easy to use them. Name of our script file “convertColorsToStatic.rb”.

Let’s call in the terminal:

ruby convertColorsToStatic.rb

Voila:

Also I’m using scripts for creating events, feature toggles, strings, architecture components (for example, VIPER) and it saves me ton of time.