Gastus API

Introduction

This API documentation is based from Highrise API

You can explore the view part of the API (everything that's fetched with GET) through a regular browser. Using Firefox for this is particularly nice as it has a good, simple XML renderer (unlike Safari which just strips the tags and dumps the content). Pretty much any URL in Gastus can be viewed in its XML form by adding the .xml extension. So /expenses/4 becomes /expenses/4.xml if you want to see the XML version.

Authentication

When you're using the API, it's always through an existing user in Gastus. So when you use the API as "john", you get to see and work with what "john" is allowed to. Authenticating is done with an authentication token, which you'll find on the "My account" screen in Gastus (click the "Reveal authentication token for API" link).

When using the authentication token, you don't need a separate password. But since Gastus uses HTTP Basic Authentication, and lots of implementations assume that you want to have a password, it's often easier just to pass in a dummy password, like X.

Example using the authentication token and a dummy password through curl:

curl -u 68444a0c7594a54be63bb0caaeecec50:X http://test.gastus.com/concepts/1.xml

Remember that anyone who has your authentication token can see and change everything you have access to. So you want to guard that as well as you guard your username and password. If you come to fear that it has been compromised, you could generate another token on the "My account" screen (click the "Reveal authentication token for API" link and then on the "Create/Renew" link).

Reading through the API

The Gastus API has two category of actions for reading: Show and list. Show returns a single record and list returns a collection. There's usually just a single show action for each resource, but many lists. All these actions are done through GET, which also means that they're all easily explorable through a browser as described above.

A few examples of reading with curl:

curl -u 68444a0c7594a54be63bb0caaeecec50:X http://test.gastus.com/expenses/3.xml
curl -u 68444a0c7594a54be63bb0caaeecec50:X http://test.gastus.com/types/53/concepts.xml

If the read is successful, you'll get an XML response back along with the status code "200 OK".

Writing through the API

Creating, updating, and deleting resources through the API is almost as easy as reading, but you can't explore it as easily through the browser. Regardless of your implementation language, though, using curl to play first is a great idea. It makes it very easy to explore the API and is perfect for small scripts too.

When you're creating and updating resources, you'll be sending XML into Gastus. You need to let the system know that fact by adding the header "Content-type: application/xml", so we know that it's not regular form-encoded data coming in. Then you just include the XML of the resource in the body of your request.

A few examples creating new resources, first with the XML inline, second referencing the XML from a file:

curl -u 68444a0c7594a54be63bb0caaeecec50:X -H 'Content-Type: application/xml' \
-d '<type><description>Vehicles</description></type>' http://test.gastus.com/types.xml
curl -u 68444a0c7594a54be63bb0caaeecec50:X -H 'Content-Type: application/xml' \
-d @expense.xml http://test.gastus.com/expenses.xml

The response to a succesful creation is the status code "201 Created". You can get the URL of the new resource in the Location header (such that you know where to update your new resource in the future).We also include the complete XML for the final resource in the response. This is because you can usually get away with creating a new resource with less than all its regular attributes. Especially attributes like created_at can be helpful to get back from the creation.

Updating resources is done through the PUT verb and against the URL of the resource you want to update. A few examples:

curl -u 68444a0c7594a54be63bb0caaeecec50:X -X PUT -H 'Content-Type: application/xml' \
-d '<concept><description>Motorbike Tyres</description></concept>' http://test.gastus.com/concepts/52.xml
curl -u 68444a0c7594a54be63bb0caaeecec50:X -X PUT -H 'Content-Type: application/xml' \
-d @expense.xml http://test.gastus.com/expenses/264.xml

The response to a successful update is "200 OK".

Finally, you can delete resources using the DELETE verb. A few examples of that:

curl -u 68444a0c7594a54be63bb0caaeecec50:X -X DELETE http://test.gastus.com/types/3.xml
curl -u 68444a0c7594a54be63bb0caaeecec50:X -X DELETE http://test.gastus.com/expenses/274.xml

Note that you don't need to pass the content-type header because you're not sending any XML. The response to a successful delete is "200 OK".

Dealing with failure

If a request fails, the error information is returned with the HTTP status code. For instance, if a requested record could not be found, the HTTP response might look something like: 

HTTP/1.1 404 The record could not be found
Date: Thu, 16 Mar 2006 17:41:40 GMT
...

Note that, if a request causes a new record to be created, the response will use the "201 Created" status. Any other successful operation (like a successful query, delete, or update) will use a 200 status code.

Alternative formats

XML is not the only other language than HTML you can make Gastus speak. We're also fairly fluent in CSV.

Conventions in the API documentation

In the documentation that follows, the following notation is used: