INHERITANCE
===========

Inheritance is useful when you have two or more reports sharing common things.

Example: two reports of Users, one with some fields and other with more fields
and landscape page orientation.

    >>> import os
    >>> cur_dir = os.path.dirname(os.path.abspath(__file__))

    >>> from django.contrib.auth.models import User

    >>> from reportlab.lib.pagesizes import A4
    >>> from reportlab.lib.units import cm
    >>> from reportlab.lib.enums import TA_CENTER, TA_RIGHT

    >>> from geraldo import Report, ReportBand, Label, ObjectValue, SystemField,\
    ...     BAND_WIDTH, landscape

Report class

    >>> class UsersReport(Report):
    ...     title = 'Users'
    ... 
    ...     class band_page_header(ReportBand):
    ...         height = 1.3*cm
    ...         elements = [
    ...             SystemField(expression='%(report_title)s', top=0.1*cm, left=0, width=BAND_WIDTH,
    ...                 style={'fontName': 'Helvetica-Bold', 'fontSize': 14, 'alignment': TA_CENTER}),
    ...             Label(text="ID", top=0.8*cm, left=0),
    ...             Label(text="Username", top=0.8*cm, left=3*cm),
    ...             Label(text="First name", top=0.8*cm, left=8*cm),
    ...             Label(text="Last name", top=0.8*cm, left=13*cm),
    ...             Label(text="Staff", top=0.8*cm, left=18*cm),
    ...         ]
    ...         borders = {'bottom': True}
    ... 
    ...     class band_page_footer(ReportBand):
    ...         height = 0.5*cm
    ...         elements = [
    ...             Label(text='Created with Geraldo Reports', top=0.1*cm),
    ...             SystemField(expression='Printed in %(now:%Y, %b %d)s at %(now:%H:%M)s', top=0.1*cm,
    ...                 width=BAND_WIDTH, style={'alignment': TA_RIGHT}),
    ...         ]
    ...         borders = {'top': True}
    ... 
    ...     class band_detail(ReportBand):
    ...         height = 0.7*cm
    ...         elements = [
    ...             ObjectValue(attribute_name='id', top=0, left=0),
    ...             ObjectValue(attribute_name='username', top=0, left=3*cm, display_format='<font size=14 name=Helvetica>%s</font>'),
    ...             ObjectValue(attribute_name='first_name', top=0, left=8*cm),
    ...             ObjectValue(attribute_name='last_name', top=0, left=13*cm),
    ...             ObjectValue(attribute_name='is_staff', top=0, left=18*cm,
    ...                 get_value=lambda instance: instance.is_staff and 'Yes' or 'No'),
    ...         ]

    >>> queryset = User.objects.order_by('id')
    >>> report = UsersReport(queryset=queryset)

PDF generation

    >>> from geraldo.generators import PDFGenerator
    >>> report.generate_by(PDFGenerator, filename=os.path.join(cur_dir, 'output/inheritance-report.pdf'))

A inheritance report class

    >>> class LandscapeUsersReport(UsersReport):
    ...     title = 'Detailed list of users'
    ...     page_size = landscape(A4)
    ... 
    ...     class band_page_footer(ReportBand):
    ...         height = 0.5*cm
    ...         elements = [
    ...             Label(text='Created with Geraldo Reports - Landscape', top=0.1*cm),
    ...             SystemField(expression='Printed in %(now:%Y, %b %d)s at %(now:%H:%M)s', top=0.1*cm,
    ...                 width=BAND_WIDTH, style={'alignment': TA_RIGHT}),
    ...         ]
    ...         borders = {'top': True}
    ... 
    ...     def __init__(self, *args, **kwargs):
    ...         super(LandscapeUsersReport, self).__init__(*args, **kwargs)
    ... 
    ...         self.band_page_header.elements += [
    ...             Label(text="Date joined", top=0.8*cm, left=21*cm),
    ...             ]
    ... 
    ...         self.band_detail.elements += [
    ...             ObjectValue(attribute_name='date_joined', top=0, left=21*cm),
    ...             ]

PDF generation

    >>> report = LandscapeUsersReport(queryset=queryset)
    >>> report.generate_by(PDFGenerator, filename=os.path.join(cur_dir, 'output/inheritance-landscape-report.pdf'))

