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Parsing Forms to Make Schemas
One obvious way to collect user requirements for a schema is to build the form, iterating it in the browser until the user approves it. If we want the form to be maintainable by the designer, then we also need to impose very few requirements on how the form is spelled.
Let's try with a really simple form:
>>> _SIMPLE_FORM = """\ ... <html> ... <body> ... <form name="simple"> ... <input type="text" name="favorite_color" value="Blue" ... title="Favorite Color" /> ... <input type="checkbox" name="likes_coffee" checked="CHECKED" /> ... <input type="radio" name="needs_haircut" value="yes" checked="CHECKED" /> ... <input type="radio" name="needs_haircut" value="no" /> ... <input type="radio" name="needs_haircut" value="maybe" /> ... <select name="plays_instrument"> ... <option value="">N/A</option> ... <option value="guitar">Guitar</option> ... <option value="bass">Bass</option> ... <option value="drums">Drums</option> ... </select> ... <textarea name="soliloquy" rows="3" cols="65" ... >To be or not to be? That is the question.</textarea> ... <textarea name="empty_text" rows="3" cols="65" ... ></textarea> ... </form> ... </body> ... </html> ... """
We would like to be able to transform that form into a schema, as:
>>> from zope.interface.interface import InterfaceClass >>> from zope.schema import Bool >>> from zope.schema import Choice >>> from zope.schema import Float >>> from zope.schema import Int >>> from zope.schema import Text >>> from zope.schema import TextLine >>> from userschema.schema import ChoiceSet >>> from userschema.schema import fromHTMLForm >>> a_schema = fromHTMLForm(_SIMPLE_FORM) >>> type(a_schema) is InterfaceClass True
If we don't override it, the __name__ of the generated interface is derived from the form element's name attribute:
>>> print a_schema.__name__ HTMLForm_simple
We can pass the 'name' to override:
>>> a_schema = fromHTMLForm(_SIMPLE_FORM, name='ISimple') >>> print a_schema.__name__ ISimple
As with the CSV-generated schema, the '__module__' attribute of the generated interface defaults to 'userschema':
>>> print a_schema.__module__ userschema
We can override that by passing 'module_name':
>>> a_schema = fromHTMLForm(_SIMPLE_FORM, module_name='somemodule') >>> print a_schema.__module__ somemodule
The attributes of the schema correspond to the form widget names:
>>> names = list(a_schema.names()) >>> names.sort() >>> print names ['empty_text', 'favorite_color', 'likes_coffee', 'needs_haircut', 'plays_instrument', 'soliloquy']
Text input widgets become TextLine fields:
>>> field = a_schema.getDescriptionFor('favorite_color')
>>> isinstance(field, TextLine)
True
>>> print field.title
Favorite Color
>>> print field.default
Blue
Checkbox widgets become Bool fields:
>>> field = a_schema.getDescriptionFor('likes_coffee')
>>> isinstance(field, Bool)
True
>>> print field.default
True
Radio button widgets become Choice fields:
>>> field = a_schema.getDescriptionFor('needs_haircut')
>>> isinstance(field, Choice)
True
>>> print field.default
yes
>>> print [str(x.value) for x in field.vocabulary]
['yes', 'no', 'maybe']
Non-multiple select widgets become Choice fields, with more metadata about the choices (both 'token' and 'value'):
>>> field = a_schema.getDescriptionFor('plays_instrument')
>>> isinstance(field, Choice)
True
>>> print field.default
None
>>> print [(str(x.value), str(x.token)) for x in field.vocabulary]
[('N/A', ''), ('Guitar', 'guitar'), ('Bass', 'bass'), ('Drums', 'drums')]
Textarea widgets become Text fields:
>>> field = a_schema.getDescriptionFor('soliloquy')
>>> isinstance(field, Text)
True
>>> print field.default
To be or not to be? That is the question.
>>> field = a_schema.getDescriptionFor('empty_text')
>>> isinstance(field, Text)
True
>>> field.default == u''
True
We can select from more than one form in the HTML by passing the name of the form:
>>> _NAMED_FORM = """\
... <html>
... <body>
... <form name="first">
... <input type="text" name="favorite_color" value="Blue" />
... </form>
... </body>
... <form name="second">
... <input type="text" name="favorite_color" value="Red" />
... </form>
... </html>
... """
>>> named_schema = fromHTMLForm(_NAMED_FORM, form_name="second")
>>> print named_schema.__name__
HTMLForm_second
>>> field = named_schema.getDescriptionFor('favorite_color')
>>> isinstance(field, TextLine)
True
>>> print field.default
Red
If we pass the name, but no form matches, fromHTMLForm raises a ValueError:
>>> fromHTMLForm(_NAMED_FORM, form_name="nonesuch") Traceback (most recent call last): ... ValueError: No matching form: nonesuch
A form which contains multiple checkboxe elements with the same name yields a field of a new type, IChoiceSet:
>>> from sets import Set as SetType
>>> from userschema.interfaces import IChoiceSet
>>> _CHOICE_SET_FORm = """\
... <html>
... <body>
... <form name="choice_set">
... <input type="checkbox" name="likes_band" value="The Beatles" />
... <input type="checkbox" name="likes_band" value="Led Zepplin"
... checked="CHECKED"/>
... <input type="checkbox" name="likes_band"
... value="Emerson, Lake, & Palmer" />
... <input type="checkbox" name="likes_band" value="The Band"
... checked="CHECKED" />
... </form>
... </html>
... """
>>> choice_set_schema = fromHTMLForm(_CHOICE_SET_FORm, form_name="choice_set")
>>> field = choice_set_schema.getDescriptionFor('likes_band')
>>> IChoiceSet.providedBy(field)
True
The default value of an IChoiceSet field is itself a set, whose elements are the values which were checked in the sample form:
>>> isinstance(field.default, SetType) True >>> len(field.default) 2 >>> 'The Beatles' in field.default False >>> 'Led Zepplin' in field.default True >>> 'Emerson, Lake & Palmer' in field.default False >>> 'The Band' in field.default True
The IChoiceSet field also has a vocabulary, made up of all the values of the checkboxes which helped define the field:
>>> vocab = field.vocabulary >>> len(vocab) 4 >>> 'The Beatles' in vocab True >>> 'Led Zepplin' in vocab True >>> 'Emerson, Lake, & Palmer' in vocab True >>> 'The Band' in vocab True
Select widgets with 'multiple' generate ChoiceSet fields:
>>> _MULTI_SELECT_FORM = """\
... <html>
... <body>
... <form name="multiselect">
... <select multiple="multiple" name="plays_instrument">
... <option value="">N/A</option>
... <option value="guitar" selected="selected">Guitar</option>
... <option value="bass" selected="selected">Bass</option>
... <option value="drums">Drums</option>
... </select>
... </form>
... </body>
... </html>
... """
>>> multiselect_schema = fromHTMLForm(_MULTI_SELECT_FORM)
>>> names = list(multiselect_schema.names())
>>> names.sort()
>>> print names
['plays_instrument']
>>> field = multiselect_schema.getDescriptionFor('plays_instrument')
>>> isinstance(field, ChoiceSet)
True
>>> isinstance(field.default, SetType)
True
>>> len(field.default)
2
>>> 'guitar' in field.default
True
>>> 'bass' in field.default
True
>>> 'drums' in field.default
False
>>> print [(str(x.value), str(x.token)) for x in field.vocabulary]
[('N/A', ''), ('Guitar', 'guitar'), ('Bass', 'bass'), ('Drums', 'drums')]
The form can also use ZPublisher's marshalling aids (':int', ':float') to signal field type:
>>> _MARSHLLED_FORM = """\
... <html>
... <body>
... <form name="multiselect">
... <input type="text" name="age:int" value="42" />
... <input type="text" name="rating:float" value="3.5" />
... </form>
... </body>
... </html>
... """
>>> marshalled_schema = fromHTMLForm(_MARSHLLED_FORM)
>>> names = list(marshalled_schema.names())
>>> names.sort()
>>> print names
['age', 'rating']
>>> field = marshalled_schema.getDescriptionFor('age')
>>> isinstance(field, Int)
True
>>> print field.default
42
>>> field = marshalled_schema.getDescriptionFor('rating')
>>> isinstance(field, Float)
True
>>> print field.default
3.5