Source Code main.rb
This is the contents of the main.rb file with the comments stripped out of it that we will be examining in this part of the tutorial.
Getting to Work
This file is the file that we loaded from the tut_hello_cube.rb extension registration file. Here is where we can write the bulk of the ruby code for our extension.
This file must be inside of a folder that has the exact same name as the registration file (without the .rb extension). In this case, the folder must be named tut_hello_cube.
Again we'll start this file by requiring the sketchup.rb file. And notice that on lines 2 and 3 we open our module so that we keep all this code wrapped cleanly inside of our own namepsace.
This method is going to be used to create a simple cube inside of a group in the model.
We need a reference to the currently active model. The SketchUp API currently only let you work on the active model. Under Windows there will be only one model open at a time, but under OS X there might be multiple models open.
Beware that if there is no model open under OS X then `active_model` will return nil. In this example we ignore that for simplicity.
Whenever you make changes to the model you must take care to use `model.start_operation` and `model.commit_operation` to wrap everything into a single undo step. Otherwise the user risk not being able to undo everything and loose work.
Making sure your model changes is undoable in a single undo step is a requirement of the Extension Warehouse submission quality checks.
Note that the first argument name is a string that will be appended to the Edit > Undo menu - so make sure you name your operations something the users can understand.
Creating a group via the API is slightly different than via the UI. Via the UI you create the faces first, then group them. But with the API you create the group first and then add it's content directly into it.
Here we define a set of 3d points to create a 1x1m face. Note that the internal unit in SketchUp is inches. This means that regardless of the model unit settings the 3d data is always stored in inches.
In order to make it easier work with lengths the Numeric class has been extended with some utility methods that let us write stuff like `1.m` to represent a meter instead of `39.37007874015748`.
We pass the points to the `add_face` method and keep the returned reference to the face as we want to keep working with it.
Note that normally the orientation (its normal) is a result of the order of the 3d points you use to create it. The exception is when you create a face on the ground plane (all points with z == 0) then it will always be face down.
Here we invoke SketchUp's push-pull functionality on the face. But note that we must use a negative number in order for it to extrude upwards in the positive direction of the Z-axis. This is because SketchUp forced this face on the ground place to be face down.
Finally we are done and we close the operation. In production you will want to catch errors and abort to clean up if your function failed. But for simplicity we won't do this here.
Here we add a menu item for the extension. Note that we again use a load guard to prevent multiple menu items from accidentally being created.
We fetch a reference to the top level menu we want to add to. Note that we use "Plugins" here which was the old name of the "Extensions" menu. By using "Plugins" you remain backwards compatible.
We add the menu item directly to the root of the menu in this example. But if you plan to add multiple items per extension we recommend you group them into a sub-menu in order to keep things organized.