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305.
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There are currently two available reflectors in Twisted Enterprise, the SQL Reflector for relational databases which uses the python DB API, and the XML Reflector which uses a file system containing XML files. The XML reflector is currently extremely slow.
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现今在 Twisted 企业框架（Twisted Enterprise）中可用的 reflectors：一是 SQL Reflector：用于关系数据库，使用的是 python 的数据库 API，另外一个是 XML Reflector：用于包含 XML 文件的文件系统，但是使用起来速度非常缓慢。
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Kevin
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Reviewed by
Fantix King
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Located in
howto/row.xhtml:102
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306.
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An example class list for the RoomRow class we specified above using the SQLReflector:
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type: Content of: <html><body><p>
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来看个例子，学习下如何通过 SQLReflector 来使用上面创建的 RoomRow：
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Located in
howto/row.xhtml:107
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307.
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from twisted.enterprise.sqlreflector import SQLReflector 
dbpool = adbapi.ConnectionPool("pyPgSQL.PgSQL")
reflector = SQLReflector( dbpool, [RoomRow] )
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from twisted.enterprise.sqlreflector import SQLReflector
dbpool = adbapi.ConnectionPool("pyPgSQL.PgSQL")
reflector = SQLReflector( dbpool, [RoomRow] )
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Fantix King
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Located in
howto/row.xhtml:111
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308.
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Creating Row Objects
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创建 RowObject（Create RowObject）
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Located in
howto/row.xhtml:117
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309.
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There are two methods of creating RowObjects - loading from the database, and creating a new instance ready to be inserted.
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type: Content of: <html><body><p>
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这里有两个方法用于创建一个 RowObject —— 从数据库中取出已有的或者是创建一个新实例并插入到数据库中。
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Located in
howto/row.xhtml:119
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310.
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To load rows from the database and create RowObject instances for each of the rows, use the loadObjectsFrom method of the Reflector. This takes a tableName, an optional <q>user data</q> parameter, and an optional <q>where clause</q>. The where clause may be omitted which will retrieve all the rows from the table. For example:
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type: Content of: <html><body><p>
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为了从数据库中取出行或者新加行，可以使用Reflector的 loadObjectsFrom 方法。她的参数包括：表名，可选的“用户数据”参数，可选的“where子句”。当然了，当你想要取出所有的行的时候，“where子句”是可以省略的。例如：
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Located in
howto/row.xhtml:122
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311.
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def gotRooms(rooms):
for room in rooms:
print "Got room:", room.id
d = reflector.loadObjectsFrom("testrooms",
whereClause=[("id", reflector.EQUAL, 5)])
d.addCallback(gotRooms)
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def gotRooms(rooms):
for room in rooms:
print "Got room:", room.id
d = reflector.loadObjectsFrom("testrooms",
whereClause=[("id", reflector.EQUAL, 5)])
d.addCallback(gotRooms)
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Translated and reviewed by
Liu, Kun
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Located in
howto/row.xhtml:130
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312.
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For more advanced RowObject construction, loadObjectsFrom may use a factoryMethod that was specified as a class attribute for the RowClass derived class. This method will be called for each of the rows with the class object, the userData parameter, and a dictionary of data from the database keyed by column name. This factory method should return a fully populated RowObject instance and may be used to do pre-processing, lookups, and data transformations before exposing the data to user code. An example factory method:
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对于更高级的 RowObject 结构，loadObjectsFrom 可以调用每个在 RowClass 子类中被声明为类属性的工厂方法(也就是上文提到的 factoyMethod)。对于每一个行对象，我们都会调用这个工厂方法（参数是类对象，用户数据以及以列名作为关键字的一个字典，其中存放了数据库中的数据）。这个工厂方法会返回一个完全组装好（fully populated）的RowObject实例，可以用来进行一些预处理，查询或者是数据格式的转换，以方便最终显示给用户。一个factory方法的例子如下：
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Located in
howto/row.xhtml:139
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313.
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def testRoomFactory(roomClass, userData, kw):
newRoom = roomClass(userData)
newRoom.__dict__.update(kw)
return newRoom |
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def testRoomFactory(roomClass, userData, kw):
newRoom = roomClass(userData)
newRoom.__dict__.update(kw)
return newRoom |
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Translated and reviewed by
Liu, Kun
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Located in
howto/row.xhtml:149
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314.
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The last method of creating a row object is for new instances that do not already exist in the database table. In this case, create a new instance and assign its primary key attributes and all of its member data attributes, then pass it to the <code>insertRow</code> method of the Reflector. For example:
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我们还需要考虑如何往一个数据表中插入一个之前并不存在的实例。在这种情况下，可以创建一个新的实例，指明它的主键，并未数据域进行赋值，然后就可以将它穿递给 Reflector 的<code>insertRow</code>方法。来看个例子：
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Reviewed by
Fantix King
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Located in
howto/row.xhtml:154
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