Command builders

1 min

The command pattern encapsulates interface actions into reusable objects. This separates execution logic from concrete widgets into a testable unit. Because commands have no reference to the UI or a visual representation, the builder pattern generates widgets from commands in a generic manner.

A command consumer (or other object responsible for displaying commands) instantiates a builder based on the desired widget type. For example, to display buttons, use a button builder.

The builders have two public methods:

create – Takes a command and a container. Builds the widget from the command and uses command properties to update the UI when the command state changes.

remove – Takes a command and a container. Removes the widget that represents the given command from the container.

Example implementation

The following example shows the button builder in use:

require([
    "dijit/Toolbar",
    "epi/shell/command/builder/ButtonBuilder",
    "epi/shell/command/ToggleCommand"
  ],
  function (Toolbar, ButtonBuilder, ToggleCommand) {
    var toolbar = new Toolbar(),
      builder = new ButtonBuilder(),
      model = {
        enabled: true
      },
      command = new ToggleCommand({
        model: model,
        property: "enabled"
      });
    builder.create(command, toolbar);
  }
);