SwiftGen Stencil template to create UIColor and UIImage extensions for all asset catalogs.

asset_extensions.stencil

/// Attention: Changes made to this file will not have any effect and will be reverted 
/// when building the project. Please adjust the Stencil template `asset_extensions.stencil` instead.
/// See https://github.com/SwiftGen/SwiftGen#bundled-templates-vs-custom-ones for more information.

import UIKit

// MARK: - Private Helper -

private final class BundleToken {}
private let bundle = Bundle(for: BundleToken.self)

{# Macro to create a static property for a given asset and class type #}
{% macro staticAsset type asset %}
static let {{asset.name|swiftIdentifier:"pretty"|lowerFirstWord|escapeReservedKeywords}} = {{type}}(named: "{{asset.value}}", in: bundle, compatibleWith: nil)!
{% endmacro %}
{# Create an UIColor extension for all color assets in asset catalogs #}
// MARK: - Colors -

extension UIColor {
    {% for catalog in catalogs %}
        {% for asset in catalog.assets %}
            {% if asset.type == "color" %}
                {% filter indent:4 %}{% call staticAsset "UIColor" asset %}{% endfilter %}
            {% endif %}
        {% endfor %}
    {% endfor %}
}

{# Create an UIImage extension for all image assets in asset catalogs #}
// MARK: - Images -

extension UIImage {
    {% for catalog in catalogs %}
        {% for asset in catalog.assets %}
            {% if asset.type == "image" %}
                {% filter indent:4 %}{% call staticAsset "UIImage" asset %}{% endfilter %}
            {% endif %}
        {% endfor %}
    {% endfor %}
}

Hey nice stencil, do you have any idea of how to adjust it so it also finds assets within a sub folder of at the asset folder? And not only in the root of the assets folder?

Hey, not sure to be honest, probably best to look at the stencil documentation or look at the templates included with SwiftGen (in case they already handle this).