Some of the Square API patterns are used across various APIs. These include the following:
- Pagination - Many Square API operations limit the size of the response. When the result of the API operation exceeds the limit, the API truncates the result. You must make a series of requests to retrieve all the data. This is referred to as pagination.
- Idempotency key - Most Square APIs that perform create, update, or delete operations require idempotency keys to protect against making duplicate calls that can have negative consequences (for example, charging a card on file twice).
- Object versioning - Some of the Square resources (for example, the
Customerobject) have versions assigned. The version numbers enable optimistic concurrency, which is the ability for multiple transactions to complete without interfering with each other.
- Clear API object fields - Square API update endpoints support an
X-Clear-Null: trueHTTP header to indicate a request containing a
These Square API patterns are exposed in the Square Ruby SDK.
Square API pagination support lets you split a full query result set into pages that are retrieved over a sequence of requests. For example, when you call
list_customers, you can limit the number of customers returned in the response. If there are more customers to retrieve, the response includes a pagination cursor. You include this cursor in your subsequent
list_customers request to retrieve the next set of customers. When the response no longer returns a cursor (the cursor is null), there are no more customers to retrieve.
The following code example calls the
list_customers method. The request limits the number of customers returned to 10. The
while loop repeats while the pagination cursor isn't null. After the first
list_customers call, the subsequent call includes the pagination cursor returned by the previous call.
When an application calls a Square API, it must be able to repeat an API operation when needed and get the same result each time. For example, if a network error occurs while updating a catalog item, the application might retry the same request and must ensure that the item updates only once.
This behavior is called idempotency. Most Square APIs that modify data (create, update, or delete) require you to provide an idempotency key that uniquely identifies the request. This allows you to retry the request if necessary, without duplicating work.
You can provide a custom unique key or simply generate one. There are language specific functions that you can use to generate unique keys. For more information, see Idempotency.
Some Square API resources support versioning. For example, each
Customer object has a version field. Initially, the version number is 0. Each update increases the version number. If you don't specify a version number in the request, the latest version is assumed.
This resource version number enables optimistic concurrency; multiple transactions can complete without interfering with each other. As a best practice, you should include the version field in the request to enable optimistic concurrency. The value must be set to the current version. For more information, see Optimistic Concurrency.
The following code example updates a customer name. The update request also includes a version number. It succeeds only if the specified version number is the latest version of the customer object on the server.
If the version numbers on the client and server don't match, the call fails with the following:
Version is not up to date.
Square supports sparse updates to resources, so you can modify only the fields that you want to change. You can also clear the existing value of a field, without replacing it with a new value. To do this, you need to add the field to the resource body, but set the field value to
null. For more information, see Clear a field with a null.
To signal that you intend to clear field values with a
null, you need to add the
X-Clear-Null: true HTTP header to your request. In the Square Ruby SDK, the
Square::Client class provides an
additional_headers parameter that you can use for this purpose.