Generate Flutter Image Asset

Generate Flutter Image Asset

Generate Flutter Image Asset


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.



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.


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.

pub global activate 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

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.

spider create --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:

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

Generate Code

Run following command to generate dart code:

spider build


path/paths* String None GROUP Where to locate assets?
class_name* String None GROUP What will be the name of generated dart class?
package String resources GLOBAL Where to generate dart code in the lib folder?
file_name String {class_name} GROUP What will be the name of the generated dart file?
prefix String None GROUP What will be the prefix of generated dart references?
types List All GROUP Which types of assets should be included?
generate_test bool false GLOBAL Generate test cases to make sure that asssets are still present inthe project?
no_comments bool false GLOBAL Removes all the generated comments from top of all generated dart code.Use this to avoid vcs noise.
export bool true GLOBAL Generates a dart file exporting all the generated classes. Can be used toavoid multiple exports.
export_file String resources.dart GLOBAL What will be the name of generated export file?
use_part_of bool false GLOBAL Allows to opt in for using part of instead of exporting generated dartfiles.

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 wanna 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.

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

Source Code

Please Visit Generate Flutter Image Asset Source Code at GitHub