CompositionΒΆ

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

But there is a big difference from Inheritance: while inheritance starts a report from the point where another one ends, composition is about you making separate things and afterwards composing a report with them.

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 PageHeaderBand(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 PageFooterBand(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 DetailBand(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 UsersReport(Report):
    """Report 1 class"""

    title = 'Users'

    band_page_header = PageHeaderBand
    band_page_footer = PageFooterBand
    band_detail = DetailBand

class LandscapeUsersReport(Report):
    """Report 2 class"""

    title = 'Users'
    page_size = landscape(A4)

    band_page_header = PageHeaderBand
    band_page_footer = PageFooterBand

    class band_detail(DetailBand):
        elements = DetailBand.elements+[
            ObjectValue(attribute_name='date_joined', top=0, left=21*cm),
        ]

    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_page_footer.elements[0].text += ' - Landscape'

Generating PDF...

>>> queryset = User.objects.order_by('id')
>>> report = UsersReport(queryset=queryset)
>>> from geraldo.generators import PDFGenerator
>>> report.generate_by(PDFGenerator, filename=os.path.join(cur_dir, 'output/composition-report.pdf'))

Now generating the composed landscape report

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

The Result