amfast文档翻译——encode and decode（编码与解码）

编码与解码

• python 内置的数据结构 和 As内置的数据结构之间的转换见：http://code.google.com/p/amfast/wiki/EncodeAndDecode#Encoder_and_Decoder上的表格

自定义的类型映射

• amfast支持用户自定义的对象类型。
• 使用 amfast.class_def.ClassDef对象，以达到用户自定义对象的序列化与反序列化。
• 使用ClassDefMapper将一个amfast.class_def.ClassDef与一个客户端的对象映射起来。

from amfast import class_def

# ClassDefMapper objects keep track of ClassDefs
class_mapper = class_def.ClassDefMapper()

# Map a custom class with static attributes
class_mapper.mapClass(class_def.ClassDef(MyCustomClass, 'class.alias', ('tuple', 'of', 'static', 'attribute', 'names')))

# Object attributes can be automatically converted
# to/from a specific type with the
# encode_types and decode_types attributes.
#
# encode_types and decode_types are dictionaries where
# the keys are the names of the attributes to convert,
# and the values are functions that will perform the conversion.
mapped_class = class_def.ClassDef(MyCustomClass, 'class.alias'....
mapped_class.encode_types = {'attribute_to_convert_to_int_before_encoding': int}
mapped_class.decode_types = {'attribute_to_convert_to_int_after_decoding': int}

# Map a custom class with dynamic attributes
class_mapper.mapClass(class_def.DynamicClassDef(MyCustomClass, 'class.alias', ()))

# Map a custom class implementing IExternalizable
# ExternClassDef must be sub-classed, and the
# methods readExternal and writeExternal must be implemented.
class_mapper.mapClass(class_def.ExternClassDef(MyCustomClass,'class.alias'))

# Map a custom class that is also mapped with SQLAlchemy.
# Attributes mapped with SQLAlchemy will automatically be
# added to the list of static attributes.
class_mapper.mapClass(class_def.sa_class_def.SaClassDef(MyCustomClass, 'class.alias')

# Attach ClassDefMapper to Encoder and Decoder
# objects to use the ClassDefMapper for encoding
# and decoding
encoder.class_def_mapper = class_mapper
decoder.class_def_mapper = class_mapper

# Use custom class mappings with a Channel
channel = channel_set.getChannel('channel_name')
channel.endpoint.encoder.class_def_mapper = class_mapper
channel.endpoint.decoder.class_def_mapper = class_mapper