There are several principles you should follow when using the Google Docs API. These include:
- Edit backwards for efficiency
- Plan for collaboration
- Ensure state consistency with
The following sections explain these principles.
Edit backwards for efficiency
Within a single call to the
BatchUpdate method, order your requests in
descending order of index location. This eliminates the need to calculate
the index changes due to insertions and deletions.
Plan for collaboration
Expect the document state to change. Between one method call and another, other collaborators might update the document, as shown in the following diagram:
This can lead to errors if your indexes are wrong. With multiple users editing
a document using the UI, Google Docs takes care of this transparently, but as
an API client your app must manage this. Even if you don't anticipate
collaboration on the document, it's important to program defensively and make
sure the document state remains consistent. For one way to ensure consistency, review the
WriteControl section below.
Ensure state consistency with WriteControl
When you read and then update a document, you can make sure the document hasn't been updated by using the
field in the
BatchUpdate method. This lets you make edits to the doc only if
the version has not changed. Here's how you use it:
- Get the document and save the
revisionIdstring that's included in it.
- Compose your update requests.
- Include a
WriteControlobject with the requiredRevisionId set to the string you saved.
- When you call
BatchUpdate, if the document revision has changed it returns an error and doesn't perform an update.