Version: Version 3.3 - Segmentation Support 🚧

Commands Manager

Overview

The CommandsManager is a class defined in the @ohif/core project. The Commands Manager tracks named commands (or functions) that are scoped to a context. When we attempt to run a command with a given name, we look for it in our active contexts. If found, we run the command, passing in any application or call specific data specified in the command's definition.

Note: A single instance of CommandsManager should be defined in the consuming application, and it is used when constructing the ExtensionManager.

A simplified skeleton of the CommandsManager is shown below:

export class CommandsManager {
  constructor({ getActiveContexts } = {}) {
    this.contexts = {};
    this._getActiveContexts = getActiveContexts;
  }

  getContext(contextName) {
    const context = this.contexts[contextName];
    return context;
  }

  /**...**/

  createContext(contextName) {
      /** ... **/
    this.contexts[contextName] = {};
  }


  registerCommand(contextName, commandName, definition) {
    /**...**/
    const context = this.getContext(contextName);
    /**...**/
    context[commandName] = definition;
  }

  runCommand(commandName, options = {}, contextName) {
    const definition = this.getCommand(commandName, contextName);
    /**...**/
    const { commandFn } = definition;
    const commandParams = Object.assign(
      {},
      definition.options, // "Command configuration"
      options // "Time of call" info
    );
    /**...**/
    return commandFn(commandParams);
  }
  /**...**/
}

Instantiating

When we instantiate the CommandsManager, we are passing two methods:

getAppState - Should return the application's state when called (Not implemented in v3)
getActiveContexts - Should return the application's active contexts when called

These methods are used internally to help determine which commands are currently valid, and how to provide them with any state they may need at the time they are called.

platform/viewer/src/appInit.js
const commandsManagerConfig = {
  getAppState: () => {},
  /** Used by commands to determine active context */
  getActiveContexts: () => [
    'VIEWER',
    'DEFAULT',
    'ACTIVE_VIEWPORT::CORNERSTONE',
  ],
};

const commandsManager = new CommandsManager(commandsManagerConfig);

Commands/Context Registration

The ExtensionManager handles registering commands and creating contexts, so you don't need to register all your commands manually. Simply, create a commandsModule in your extension, and it will get automatically registered in the context provided.

A simplified version of this registration is shown below to give an idea about the process.

export default class ExtensionManager {
  constructor({ commandsManager }) {
    this._commandsManager = commandsManager
  }
  /** ... **/
  registerExtension = (extension, configuration = {}, dataSources = []) => {
    let extensionId = extension.id
    /** ... **/

    // Register Modules provided by the extension
    moduleTypeNames.forEach((moduleType) => {
      const extensionModule = this._getExtensionModule(
        moduleType,
        extension,
        extensionId,
        configuration
      )

      if (moduleType === 'commandsModule') {
        this._initCommandsModule(extensionModule)
      }
      /** registering other modules **/
    })
  }

  _initCommandsModule = (extensionModule) => {
    let { definitions, defaultContext } = extensionModule
    defaultContext = defaultContext || 'VIEWER'

    if (!this._commandsManager.getContext(defaultContext)) {
      this._commandsManager.createContext(defaultContext)
    }

    Object.keys(definitions).forEach((commandName) => {
      const commandDefinition = definitions[commandName]
      const commandHasContextThatDoesNotExist =
        commandDefinition.context &&
        !this._commandsManager.getContext(commandDefinition.context)

      if (commandHasContextThatDoesNotExist) {
        this._commandsManager.createContext(commandDefinition.context)
      }

      this._commandsManager.registerCommand(
        commandDefinition.context || defaultContext,
        commandName,
        commandDefinition
      )
    })
  }
}

If you find yourself in a situation where you want to register a command/context manually, ask yourself "why can't I register these commands via an extension?", but if you insist, you can use the CommandsManager API to do so:

// Command Registration
commandsManager.registerCommand('context', 'name', commandDefinition);

// Context Creation
commandsManager.createContext('string');