A small dart library to generate Assets dart code from assets folder.





A small dart library to generate Assets dart code from assets folder. It generates dart class with static const variables in it which can be used to reference the assets safely anywhere in the flutter app.

Build Tests codecov Pub Version

User Guide: Spider Docs

Breaking Changes since v4.0.0:

  • --info flag command is now --about command.
  • --check-updates flag command is now --check-for-updates.



Widget build(BuildContext context) {
  return Image(image: AssetImage('assets/background.png'));


Widget build(BuildContext context) {
  return Image(image: AssetImage(Assets.background));

Generated Assets Class

class Assets {
  static const String background = 'assets/background.png';

This method allows no error scope for string typos. Also, it provides auto-complete in the IDE which comes very handy when you have large amount of assets.


Install using pub

This is package is an independent library that is not linked to your project. So there's no need to add it to your flutter project as it works as a global command line tool for all of your projects.

dart pub global activate spider

Install using Homebrew

brew tap birjuvachhani/spider
brew install spider

Run following command to see help:

spider --help


Create Configuration File

Spider provides a very easy and straight forward way to create a configuration file. Execute following command, and it will create a configuration file with default configurations in it.

spider create

To append configs in pubspec.yaml file, execute following command.

spider create --add-in-pubspec

To use a custom directory path for configuration file, execute following command.

spider create -p ./directory/path/for/config

Now you can modify available configurations and Spider will use those configs when generating dart code.

Use JSON config file

Though above command creates YAML format for config file, spider also supports JSON format for config file. Use this command to create JSON config file instead of YAML.

# Create in root directory
spider create --json

# or

# custom directory path
spider create -p ./directory/path/for/config --json

No matter which config format you use, JSON or YAML, spider automatically detects it and uses it for code generation.

Here's the default configuration that will be in the config file:

# Generated by Spider

# Generates unit tests to verify that the assets exists in assets directory
generate_tests: true

# Use this to remove vcs noise created by the `generated` comments in dart code
no_comments: true

# Exports all the generated file as the one library
export: true

# This allows you to import all the generated references with 1 single import!
use_part_of: true

# Location where all the generated references will be stored
package: resources

  - path: assets/images
    class_name: Images
    types: [ .png, .jpg, .jpeg, .webp, .webm, .bmp ]

Generate Code

Run following command to generate dart code:

spider build

If you're using custom directory path for the configuration file, then you can specify the config file path like this:

spider -p ./path/to/config/file/spider.yaml build



Watch Directory

Spider can also watch given directory for changes in files and rebuild dart code automatically. Use following command to watch for changes:

spider build --watch

see help for more information:

spider build --help

Smart Watch (Experimental)

The normal --watch option watches for any kind of changes that happens in the directory. However, this can be improved my smartly watching the directory. It includes ignoring events that doesn't affect anything like file content changes. Also, it only watches allowed file types and rebuilds upon changes for those files only.

Run following command to watch directories smartly.

spider build --smart-watch

Categorizing by File Extension

By default, Spider allows any file to be referenced in the dart code. but you can change that behavior. You can specify which files you want to be referenced.

path: assets
class_name: Assets
package: res
types: [ jpg, png, jpeg, webp, bmp, gif ]

Use Prefix

You can use prefixes for names of the generated dart references. Prefixes will be attached to the formatted reference names.

path: assets
class_name: Assets
package: res
prefix: ic
class Assets {
  static const String icCamera = 'assets/camera.png';
  static const String icLocation = 'assets/location.png';

Advanced Configuration

Spider provides supports for multiple configurations and classifications. If you want to group your assets by module, type or anything, you can do that using groups in spider.


Suppose you have both vector(SVGs) and raster images in your project, and you want to me classified separately so that you can use them with separate classes. You can use groups here. Keep your vector and raster images in separate folder and specify them in the config file.


  - path: assets/images
    class_name: Images
    package: res
  - path: assets/vectors
    class_name: Svgs
    package: res

Here, first item in the list indicates to group assets of assets/images folder under class named Images and the second one indicates to group assets of assets/vectors directory under class named Svgs.

So when you refer to Images class, auto-complete suggests raster images only, and you know that you can use them with AssetImage and other one with vector rendering library.

Multi-path configuration

From Spider v0.4.0, multiple paths can be specified for a single group to collect references from multiple directories and generate all the references under single dart class.


  - paths:
      - assets/images
      - assets/more_images/
    class_name: Images
    package: res
    types: [ .png, .jpg, .jpeg, .webp, .webm, .bmp ]

By using paths, multiple source directories can be specified. Above example will generate references from assets/images and assets/more_images/ under a single dart class named Images.

Generating Tests

Spider v0.4.0 adds support for generating test cases for generated dart references to make sure that the asset file is present in the project. These tests can also be run on CI servers. To enable tests generation, specify generate_tests flag in spider.yaml or spider.json configuration file as shown below.

generate_tests: true

This flag will indicate spider to generate tests for all the generated dart references.

Generate values list

Familiar with Enum.values list which contains all the enum values? Spider also provides support for generating values list for all the asset references in given dart class. Use use_references_list global config to enable values list generation. This is disabled by default as it can be overwhelming to have this code-gen if you don't need it.

# global config
use_references_list: true

Enable Verbose Logging

Spider prefers not to overwhelm terminal with verbose logs that are redundant for most of the cases. However, those verbose logs come quite handy when it comes to debug anything. You can enable verbose logging by using --verbose option on build command.

spider build --verbose

# watching directories with verbose logs
spider build --watch --verbose

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Copyright © 2020 Birju Vachhani

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at


Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
See the License for the specific language governing permissions and
limitations under the License.