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CouchDB: The Definitive Guide
book

CouchDB: The Definitive Guide

by J. Chris Anderson, Jan Lehnardt, Noah Slater
January 2010
Intermediate to advanced content levelIntermediate to advanced
272 pages
6h 41m
English
O'Reilly Media, Inc.
Content preview from CouchDB: The Definitive Guide

Chapter 7. Validation Functions

In this chapter, we look closely at the individual components of Sofa’s validation function. Sofa has the basic set of validation features you’ll want in your apps, so understanding its validation function will give you a good foundation for others you may write in the future.

CouchDB uses the validate_doc_update function to prevent invalid or unauthorized document updates from proceeding. We use it in the example application to ensure that blog posts can be authored only by logged-in users. CouchDB’s validation functions—like map and reduce functions—can’t have any side effects; they run in isolation of a request. They have the opportunity to block not only end-user document saves, but also replicated documents from other CouchDBs.

Document Validation Functions

To ensure that users may save only documents that provide these fields, we can validate their input by adding another member to the _design/ document: the validate_doc_update function. This is the first time you’ve seen CouchDB’s external process in action. CouchDB sends functions and documents to a JavaScript interpreter. This mechanism is what allows us to write our document validation functions in JavaScript. The validate_doc_update function gets executed for each document you want to create or update. If the validation function raises an exception, the update is denied; when it doesn’t, the updates are accepted.

Document validation is optional. If you don’t create a validation function, no ...

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Publisher Resources

ISBN: 9780596158156Errata Page