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LoopBack 4 provides command-line tools to help you get started quickly. The command line tools generate application and extension projects and install their dependencies for you. The CLI can also help you generate artifacts, such as controllers, for your projects. Once generated, the scaffold can be expanded with users’ own code as needed.

To use LoopBack 4’s CLI, run this command:

npm install -g @loopback/cli

Generating LoopBack projects

Commands Description See
lb4 Create a new LoopBack4 application Application generator
lb4 extension Create a new LoopBack4 extension Extension generator
lb4 update Check and/or update project dependencies of LoopBack modules Project dependency update
lb4 copyright Add or update copyright/license header for JavaScript/TypeScript files Copyright generator
lb4 example Download one of LoopBack example projects Download examples

Generating LoopBack artifacts

Commands Description See
lb4 controller Add a new controller to a LoopBack 4 application Controller generator
lb4 datasource Add a new datasource to a LoopBack 4 application DataSource generator
lb4 import-lb3-models Import one or more LoopBack 3 models to a LoopBack 4 application Importer for LoopBack 3 models
lb4 model Add a new model to a LoopBack 4 application Model generator
lb4 relation Add a relation between two models in a LoopBack 4 application Relation generator
lb4 repository Add new repositories for selected model(s) to a LoopBack 4 application Repository generator
lb4 service Add a new remote or local service to a LoopBack 4 application Service generator
lb4 openapi Generate controllers and models from OpenAPI specs OpenAPI generator
lb4 discover Discover models from relational databases Model Discovery
lb4 observer Generate life cycle observers for application start/stop Life cycle observer generator
lb4 interceptor Generate interceptors Global interceptor generator
lb4 rest-crud Generate rest configs for model endpoints Model endpoint generator

Upgrading LoopBack dependencies

When the application is initially scaffolded with lb4 command, we add the cli version to .yo.rc.json:

{
  "@loopback/cli": {
    "version": "1.21.4"
  }
}

To find a compatible list of LoopBack modules for a given version of cli, run:

lb4 -v

It prints out compatible modules that are released with the current version of cli.

@loopback/cli version: 1.23.1

@loopback/* dependencies:
  - @loopback/authentication: ^3.1.1
  - @loopback/boot: ^1.5.8
  - @loopback/build: ^2.0.13
  - @loopback/context: ^1.23.2
  - @loopback/core: ^1.10.4
  - @loopback/metadata: ^1.3.4
  - @loopback/openapi-spec-builder: ^1.2.15
  - @loopback/repository-json-schema: ^1.10.2
  - @loopback/repository: ^1.15.1
  - @loopback/rest: ^1.20.1
  - @loopback/testlab: ^1.9.1
  - @loopback/docs: ^2.2.1
  - @loopback/example-hello-world: ^1.2.16
  - @loopback/example-log-extension: ^1.2.16
  - @loopback/example-rpc-server: ^1.2.16
  - @loopback/example-todo: ^1.8.2
  - @loopback/example-soap-calculator: ^1.6.17
  - @loopback/service-proxy: ^1.3.8
  - @loopback/http-caching-proxy: ^1.1.15
  - @loopback/http-server: ^1.4.15
  - @loopback/example-todo-list: ^1.11.1
  - @loopback/dist-util: ^0.4.0
  - @loopback/rest-explorer: ^1.4.1
  - @loopback/eslint-config: ^4.1.1
  - @loopback/example-express-composition: ^1.7.1
  - @loopback/example-greeter-extension: ^1.3.16
  - @loopback/booter-lb3app: ^1.3.2
  - @loopback/example-lb3-application: ^1.1.16
  - @loopback/example-greeting-app: ^1.2.2
  - @loopback/example-context: ^1.2.16
  - @loopback/repository-tests: ^0.5.1
  - @loopback/health: ^0.2.8
  - @loopback/authorization: ^0.4.1
  - @loopback/rest-crud: ^0.3.2
  - @loopback/security: ^0.1.4
  - @loopback/authentication-passport: ^1.0.1

Once a project is generated, running lb4 commands on the project checks if the project has incompatible versions with the current cli and prompts users to proceed or exit.

To update dependencies in the package.json, you can use npm update or npm-check. The existing application may be broken due to dependency changes. Please make sure build/test/run are still passing after the upgrade.

Install shell autocompletion

To enable shell autocompletion with the tab key:

lb4 install-completion
? Which Shell do you use ? (Use arrow keys)
❯ bash
  zsh
  fish
? Which Shell do you use ? bash
? We will install completion to ~/.bashrc, is it ok ? Yes
=> Tabtab line already exists in ~/.config/tabtab/__tabtab.bash file
=> Tabtab line already exists in ~/.bashrc file
=> Wrote completion script to /Users/<user>/.config/tabtab/lb4.bash file

      => Tabtab source line added to ~/.bashrc for lb4 package.

      Make sure to reload your SHELL.

Now you can type lb4 followed by pressing the tab keys twice to be prompted for auto completion, including commands and options.

$ lb4
app                example            observer           service
controller         extension          openapi            update
copyright          import-lb3-models  relation
datasource         interceptor        repository
discover           model              rest-crud

$ lb4 controller --
--ask-answered    --force-install   --skip-cache
--config          --format          --skip-install
--controllerType  --help            --yes

To uninstall it, run:

lb4 uninstall-completion

Naming Convention

LoopBack 4 uses different convention for naming classes, variables, and files.

  • Class name: PascalCase.
  • File name: kebab-case.
  • Variable name: camelCase.

Here are some examples:

Input Case Class Name Model File Names
MyModel Input remains the same MyModel my-model.model.ts
my_model Underscores get removed MyModel my-model.model.ts
mymódel Accented characters get replaced Mymodel mymodel.model.ts
Car4share Input contains digits Car4Share car-4-share.model.ts
MyModel2 Input ends with digits MyModel2 my-model2.model.ts
My-Model Class name cannot contain some symbols Invalid Invalid
4user Class name cannot start with a number Invalid Invalid