title: SyncAdaptorModules
tags: internals

! Introduction

SyncAdaptorModules encapsulate storage mechanisms that can be used by the SyncMechanism. Two examples are:

* The TiddlyWebAdaptor interfaces with servers compatible with TiddlyWeb's HTTP API, such as TiddlyWeb itself and TiddlyWiki5's built-in ServerMechanism.

* The LocalFileAdaptor interfaces with file systems with an API compatible with node.js's `fs` module

SyncAdaptorModules are represented as JavaScript tiddlers with the field `module-type` set to `syncadaptor`.

! Exports

The following properties should be exposed via the `exports` object:

|!Property |!Description |
|adaptorClass |The JavaScript class for the adaptor |

Nothing should be exported if the adaptor detects that it isn't capable of operating successfully (eg, because it only runs on either the browser or the server, or because a dependency is missing).

! Adaptor Module Methods

Adaptor modules must handle the following methods.

!! `Constructor(syncer)`

Initialises a new adaptor instance.

|!Parameter |!Description |
|syncer |Syncer object that is using this adaptor |

!! `getTiddlerInfo(tiddler)`

Gets the supplemental information that the adaptor needs to keep track of for a particular tiddler. For example, the TiddlyWeb adaptor includes a `bag` field indicating the original bag of the tiddler.

|!Parameter |!Description |
|tiddler |Target tiddler |

Returns an object storing any additional information required by the adaptor.

!! `getStatus(callback)`

Retrieves status information from the server.

|!Parameter |!Description |
|callback |Callback function invoked with parameters `err,isLoggedIn,userName` |

!! `login(username,password,callback)`

Attempts to login to the server with specified credentials.

|!Parameter |!Description |
|username |Username |
|password |Password |
|callback |Callback function invoked with parameter `err` |

!! `logout(callback)`

Attempts to logout of the server.

|!Parameter |!Description |
|callback |Callback function invoked with parameter `err` |

!! `getSkinnyTiddlers(callback)`

Retrieves a list of skinny tiddlers from the server.

|!Parameter |!Description |
|callback |Callback function invoked with parameter `err,tiddlers`, where `tiddlers` is an array of tiddler field objects |

!! `saveTiddler(tiddler,callback)`

Saves a tiddler to the server.

|!Parameter |!Description |
|tiddler |Tiddler to be saved |
|callback |Callback function invoked with parameter `err,adaptorInfo,revision` |

!! `loadTiddler(title,callback)`

Loads a tiddler from the server.

|!Parameter |!Description |
|title |Title of tiddler to be retrieved |
|callback |Callback function invoked with parameter `err,tiddlerFields` |

!! `deleteTiddler(title,callback)`

Delete a tiddler from the server.

|!Parameter |!Description |
|title |Title of tiddler to be deleted |
|callback |Callback function invoked with parameter `err` |