SQLAlchemy comes with a default set of field types that can be used. These field types will trigger the use of certain delegates and editors to visualize them in the views. Camelot extends those SQLAlchemy field types with some of its own.
An overview of field types from SQLAlchemy and Camelot is given in the table below :
Field types handled through introspection :
Field type | Default delegate | Default editor |
BOOLEAN | BoolDelegate | ![]() |
Boolean | BoolDelegate | ![]() |
Code | CodeDelegate | ![]() |
Color | ColorDelegate | ![]() |
Date | DateDelegate | ![]() |
DateTime | DateTimeDelegate | ![]() |
Enumeration | EnumerationDelegate | ![]() |
File | FileDelegate | ![]() |
Float | FloatDelegate | ![]() |
INTEGER | IntegerDelegate | ![]() |
IPAddress | CodeDelegate | ![]() |
Image | ImageDelegate | ![]() |
Integer | IntegerDelegate | ![]() |
Language | LanguageDelegate | ![]() |
Numeric | FloatDelegate | ![]() |
Rating | StarDelegate | ![]() |
RichText | RichTextDelegate | ![]() |
String | PlainTextDelegate | ![]() |
TEXT | PlainTextDelegate | ![]() |
Time | TimeDelegate | ![]() |
Unicode | PlainTextDelegate | ![]() |
VirtualAddress | VirtualAddressDelegate | ![]() |
SQLAlchemy provides a number of field types that map to available data types in SQL, more information on those can be found on the SQLAlchemy website .
The types used mosed common are :
A bool datatype.
Boolean typically uses BOOLEAN or SMALLINT on the DDL side, and on the Python side deals in True or False.
A type for datetime.date() objects.
A type for datetime.datetime() objects.
Date and time types return objects from the Python datetime module. Most DBAPIs have built in support for the datetime module, with the noted exception of SQLite. In the case of SQLite, date and time types are stored as strings which are then converted back to datetime objects when rows are returned.
A type for float numbers.
Returns Python float objects by default, applying conversion as needed.
A type for int integers.
A type for fixed precision numbers.
Typically generates DECIMAL or NUMERIC. Returns decimal.Decimal objects by default, applying conversion as needed.
A type for datetime.time() objects.
A variable length Unicode string.
The Unicode type is a String which converts Python unicode objects (i.e., strings that are defined as u'somevalue') into encoded bytestrings when passing the value to the database driver, and similarly decodes values from the database back into Python unicode objects.
It’s roughly equivalent to using a String object with convert_unicode=True, however the type has other significances in that it implies the usage of a unicode-capable type being used on the backend, such as NVARCHAR. This may affect what type is emitted when issuing CREATE TABLE and also may effect some DBAPI-specific details, such as type information passed along to setinputsizes().
When using the Unicode type, it is only appropriate to pass Python unicode objects, and not plain str. If a bytestring (str) is passed, a runtime warning is issued. If you notice your application raising these warnings but you’re not sure where, the Python warnings filter can be used to turn these warnings into exceptions which will illustrate a stack trace:
import warnings
warnings.simplefilter('error')
Bytestrings sent to and received from the database are encoded using the dialect’s encoding, which defaults to utf-8.
Camelot extends the SQLAlchemy field types with a number of its own field types. Those field types are automatically mapped to a specific delegate taking care of the visualisation.
Those fields are stored in the camelot.types module.
SQLAlchemy column type to store codes. Where a code is a list of strings on which a regular expression can be enforced.
This column type accepts and returns a list of strings and stores them as a string joined with points.
eg: ['08', 'AB'] is stored as 08.AB
alias of Unicode
The Color field returns and accepts tuples of the form (r,g,b,a) where r,g,b,a are integers between 0 and 255. The color is stored as an hexadecimal string of the form AARRGGBB into the database, where AA is the transparency, RR is red, GG is green BB is blue:
class MovieType(Entity):
color = Field(camelot.types.Color())
The colors are stored in the database as strings.
Use:
QColor(*color)
to convert a color tuple to a QColor.
alias of Unicode
The enumeration field stores integers in the database, but represents them as strings. This allows efficient storage and querying while preserving readable code.
Typical use of this field would be a status field.
Enumeration fields are visualized as a combo box, where the labels in the combo box are the capitalized strings:
class Movie(Entity):
title = Field(Unicode(60), required=True)
state = Field(camelot.types.Enumeration([(1,'planned'), (2,'recording'), (3,'finished'), (4,'canceled')]),
index=True, required=True, default='planning')
If None should be a possible value of the enumeration, add (None, None) to the list of possible enumerations. None will be presented as empty in the GUI.
alias of Integer
Sqlalchemy column type to store files. Only the location of the file is stored
This column type accepts and returns a StoredFile. The name of the file is stored as a string in the database. A subdirectory upload_to can be specified:
class Movie(Entity):
script = Field(camelot.types.File(upload_to='script'))
Retrieving the actual storage from a File field can be a little cumbersome. The easy way is taking it from the field attributes, in which it will be put by default. If no field attributes are available at the location where the storage is needed, eg in some function doing document processing, one needs to go through SQLAlchemy to retrieve it.
For an ‘task’ object with a File field named ‘document’, the storage can be retrieved:
from sqlalchemy import orm
task_mapper = orm.object_mapper( task )
document_property = task_mapper.get_property('document')
storage = document_property.columns[0].type.storage
alias of Unicode
alias of StoredFile
Sqlalchemy column type to store images
This column type accepts and returns a StoredImage, and stores them in the directory specified by settings.CAMELOT_MEDIA_ROOT. The name of the file is stored as a string in the database.
The Image field type provides the same functionallity as the File field type, but the files stored should be images.
alias of StoredImage
The languages are stored as a string in the database of the form language[_country], where :
- language is a lowercase, two-letter, ISO 639 language code,
- territory is an uppercase, two-letter, ISO 3166 country code
This used to be implemented using babel, but this was too slow and used too much memory, so now it’s implemented using QT.
alias of Unicode
The rating field is an integer field that is visualized as a number of stars that can be selected:
class Movie(Entity):
title = Field(Unicode(60), required=True)
rating = Field(camelot.types.Rating())
alias of Integer
RichText fields are unlimited text fields which contain html. The html will be rendered in a rich text editor.
alias of UnicodeText
A single field that can be used to enter phone numbers, fax numbers, email addresses, im addresses. The editor provides soft validation of the data entered. The address or number is stored as a string in the database.
This column type accepts and returns tuples of strings, the first string is the virtual_address_type, and the second the address itself.
eg: ('email','project-camelot@conceptive.be') is stored as email://project-camelot@conceptive.be
alias of Unicode