Inheritance
===========

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

Example: two reports of Users, one with some fields and another 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
    
    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'),
            ]
    
    class LandscapeUsersReport(UsersReport):
        """An inheritance report class"""
    
        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),
                ]

Generating PDF...

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

The Result

- http://geraldo.svn.sourceforge.net/viewvc/geraldo/examples/inheritance-landscape-report.pdf

