How to access asset catalogs from your Xcode project.

access_catalogs.py

# !/usr/bin/python3

"""
 Asset catalogs are not accessible in your Xcode project because they are compiled archive (.car files) so doing
 something like Bundle.main.url().. won't work.
 
"""

"""
 1. Manually add a file colors.json to your Xcode project on the level ${PROJECT_DIR}/project_name/<here> and 
 add it as a member of the target.
 2. Add this script in ${PROJECT_DIR}/<here>.
 3. Add a new Xcode Build Phase Run Script ( python3 ${PROJECT_DIR}/access_catalogs.py ).
 4. This script collects colors name from ${PROJECT_DIR}/SomeAssetCatalog.xcassets and generates colors.json file ( or overwrite )
 which is already present in Xcode bundle and is a member of the target ( done in step 1 ).
 
"""

import os
import sys
import json

json_file = "colors.json"
color_set_extension = ".colorset"
color_path = "project_name/SomeAssetCatalog.xcassets"

def check_for_paths():
    if not os.path.exists(color_path):
        print(f"{color_path} does not exist.", file= sys.stderr)
        exit(1)

# ignore files like .DS_Store or Contents.json
def remove_extra_files(file_name: str) -> bool:
    if color_set_extension in file_name:
        return True
    return False

# remove .colorset extension for all files
def remove_extension(file_name: str) -> str:
    index = file_name.index(color_set_extension)
    return file_name[: index]

def main():
    check_for_paths()

    abs_path = os.path.abspath(".")
    os.chdir(color_path)

    all_files = os.listdir(".")
    color_set_files = filter(remove_extra_files, all_files)
    removed_extension_file_names = map(remove_extension, color_set_files)

    final_files_list = list(removed_extension_file_names)
    final_files_list.sort()

    payload = {
        "colors": final_files_list
    }

    os.chdir("../")

    with open(json_file, mode= "w") as path:
        json.dump(payload, path, indent= 4)

if __name__ == "__main__":
    main()