class-config

The config package to define and read the configuration.

Prepare

This package just support Typescript.

You should install reflect-metadata package. And set follow code on tsconfig.json.

// tsconfig.json
{
  "compilerOptions": {
    ...
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    ...
  }
}

Usage

Define a config class

First, You can use @Config define your configuration class. Next, use @ConfigField defined a configuration field.

import 'reflect-metadata';
import { BaseConfig, Config, ConfigField } from '@class-config/core';

@Config()
class Configuration extends BaseConfig {
  /**
   * The server host
   */
  @ConfigField()
  public host!: string;

  /**
   * The server port
   */
  @ConfigField()
  public port!: number;
}

Config Source

The 'config source' specifies how to load the config data from. Below are some config sources:

• @class-config/source-env

You can use @From load config field from a config source.

For example:

import 'reflect-metadata';
import { BaseConfig, Config, ConfigField, From } from '@class-config/core';
import { Env } from '@class-config/source-env';

process.env.SERVER_HOST = 'localhost';
process.env.SERVER_PORT = '8080';

@Config()
class Configuration extends BaseConfig {
  /**
   * The server host
   */
  @ConfigField()
  @From(new Env('SERVER_HOST'))
  public host!: string;

  /**
   * The server port
   */
  @ConfigField()
  @From(new Env('SERVER_PORT'))
  public port!: number;
}

// configuration = { "host": "localhost", "port": 8080 }
const configuration = await Configuration.init<Configuration>();

Default value

You can use @DefaultValue load config field by default value.

For example:

import 'reflect-metadata';
import { BaseConfig, Config, ConfigField, DefaultValue } from '@class-config/core';

@Config()
class Configuration extends BaseConfig {
  /**
   * The server host
   */
  @ConfigField()
  @DefaultValue('localhost')
  public host!: string;

  /**
   * The server port
   */
  @ConfigField()
  @DefaultValue(8080)
  public port!: number;
}

// configuration = { "host": "localhost", "port": 8080 }
const configuration = await Configuration.init<Configuration>();

Customize parser

You can customize a field's parser by @ClassField

@Config()
class DatabaseConfig extends BaseConfig {
  /**
   * Database hosts
   */
  @ConfigField({
    parser: (value) => value.split(','),
  })
  @From(new Env('HOSTS'))
  public hosts!: string[];
}

// configuration = { "hosts": ["127.0.0.1", "127.0.0.2"] }
const configuration = await DatabaseConfig.init<DatabaseConfig>();

Validator

The validator will check if your config file is valid. Below is some validator.

• @class-config/validator-class

You can't set validator by init.

For example:

import 'reflect-metadata';
import { BaseConfig, Config, ConfigField, DefaultValue } from '@class-config/core';
import { ClassValidator } from '@class-config/validator-class';
import { IsString, IsNumber } from 'class-validator';

@Config()
class Database extends BaseConfig {
  /**
   * The server host
   */
  @ConfigField()
  @DefaultValue('localhost')
  @IsString()
  public host!: string;

  /**
   * The server port
   */
  @ConfigField()
  @DefaultValue('8080')
  @IsNumber()
  public port!: number;
}

const config = await Database.init<Database>({
  validator: new ClassValidator(),
});

Example

Basic

import 'reflect-metadata';
import { BaseConfig, Config, ConfigField, DefaultValue, From } from '@class-config/core';
import { Env } from '@class-config/source-env';

@Config()
class Configuration extends BaseConfig {
  /**
   * The server host
   */
  @ConfigField()
  @From(new Env('SERVER_HOST'))
  @DefaultValue('localhost')
  public host!: string;

  /**
   * The server port
   */
  @ConfigField()
  @From(new Env('SERVER_PORT'))
  @DefaultValue('8080')
  public port!: number;
}

// configuration = { "host": "localhost", "port": 8080 }
const configuration = await Configuration.init<Configuration>();

Nested

import 'reflect-metadata';
import { BaseConfig, Config, ConfigField, DefaultValue, From } from '@class-config/core';
import { Env } from '@class-config/source-env';

@Config()
class Database extends BaseConfig {
  /**
   * The server host
   */
  @ConfigField()
  @From(new Env('SERVER_HOST'))
  @DefaultValue('localhost')
  public host!: string;

  /**
   * The server port
   */
  @ConfigField()
  @From(new Env('SERVER_PORT'))
  @DefaultValue('8080')
  public port!: number;
}

@Config()
class Configuration {
  /**
   * Database config
   */
  @ConfigField()
  public database!: Database;
}

// configuration = { "database: { "host": "localhost", "port": 8080 } }
const configuration = await Configuration.init<Configuration>();

More Information

• @class-config/core
• @class-config/source-env
• @class-config/validator-class