This article explains how to work with the two most common types of objects in r2slides: presentation and slide.
The first step in any workflow with r2slides is to create a presentation object. This can be done with the new_presentation() or register_presentation() functions. new_presentation() takes the name of a presentation you want to create and creates it in your Google Drive. register_presentation() takes a presentation ID, URL, name, or 1 row dribble object (see the excellent googledrive package) and registers it for use in r2slides.
presentation <- new_presentation(title = "My Presentation")
presentation2 <- register_presentation("Already existing presentation")Note
The first time you run a function that uses r2slides, the authentication flow will start. It should take you to a browser and have you authorize r2slides to access your Google Drive. See
authenticationfor more information.
Presentation Class
The Presentation class includes several helpful fields and methods. Here are a few that you are most likely to interact with:
presentation$title # Returns the title of the presentation
presentation$last_refreshed # Returns the last time the presentation was refreshed from Google Drive
presentation$browse() # Opens the presentation in a browser
presentation$refresh() # Refreshes the presentation from Google Drive to sync changes
presentation$get_url() # Returns the URL of the presentation
presentation$copy() # Creates a copy of the presentation in Google Drive
print(presentation) # Prints a summary of the presentationPresentations are pretty unique objects that behave differently than most objects you are used to. This is because presentation objects are R6 objects that use reference semantics. This means that the object is not copied on modification. In other words, when you move, modify, or copy a r2slides::presentation object, the change is reflected everywhere that object is bound.
The reference semantics enable some pretty cool behavior. You may have noticed in new_presentation() and register_presentation() an argument called set_active. When this is TRUE (the default) the presentation object is set as the active presentation. This means for the most part you don’t have to specify presentation for anything, it will automatically grab the presentation object. You can always check if a presentation is active by calling presentation$is_active or print(presentation). Alternatively, you can call get_active_presentation() to retrieve the current active presentation object.
Slide Class
Slides are the backbones of r2slides. At its core, a slide object contains a reference to a presentation object and a unique identifier that points to the correct slide.
There are a variety of slide selection helpers that can be used to create slide objects.
on_slide_url("<URL GOES HERE>") # Creates a slide object from a URL
on_slide_id("slide_id") # Creates a slide object from a slide ID
on_slide_number(2) # Creates a slide object that references the 2nd slide in a presentation
on_slide_after(slide) # Creates a slide object that references the slide after the reference slide
on_slide_after(slide, offset = -1) # Creates a slide object that references the slide before the reference slide. Offset in the number of slides after the reference slide.While you can pass a presentation object to all of these functions (and you should if you are working with multiple presentations in the same R session), if you are editing only one presentations at a time, you can omit the presentation argument and it will default to the active presentation.
Slide objects have a couple other goodies that you might find helpful. You can use the == operator to compare slides. This will return TRUE if the two slides are duplicated of each other (that is, every item on the slide is exactly equivalent). You can also use the print() function to print a summary of the slide. In addition, slide objects have a few other fields that are only calculated when you access them. These are mainly used internally and are not intended for direct use.