Question

I am new to CherryPy. I am using the default dispatcher, with a URL structure similar to this:

root = Root()
root.page1 = Page1()
root.page1.apple = Apple()
root.page2 = Page2()
root.page2.orange = Orange()

Orange renders a template, in which I need a link to Apple. I could just hardcode /page1/apple/. But how can I get the URL of Apple in a DRY manner?

Can this be done with the default dispatcher in CherryPy, or is it only possible with the Routes dispatcher?

(I am coming from the Django world, where one would use reverse() for this purpose.)

Answer 1

You can access to the mounted apps through

cherrypy.tree.apps[mount_point].root

root is always the mounted instance to the mount point. So a reverse function would look like:

def reverse(cls):
    # get link to a class type
    for app_url in cherrypy.tree.apps.keys():
        if isinstance(cherrypy.tree.apps[app_url].root, cls):
            # NOTE: it will return with the first mount point of this class
            return app_url

Please find a sample code below that uses your classes. http://localhost:8080/page4/orange/ prints out { Orange and the link to apple: : "/page3/apple" }

import cherrypy

link_to_apple_global = ''

class Orange(object):
    def __init__(self):
        pass
    @cherrypy.expose
    @cherrypy.tools.json_out()
    def index(self):
        return {"Orange and the link to apple: ": link_to_apple_global}
class Page2(object):

    def __init__(self):
        pass
    @cherrypy.expose
    def index(self):
        return "Page2"
class Apple(object):

    def __init__(self):
        pass
    @cherrypy.expose
    def index(self):
        return "Apple"

class Page1(object):

    def __init__(self):
        pass
    @cherrypy.expose
    def index(self):
        return "Page1"

class Root(object):

    def __init__(self):
        pass
    @cherrypy.expose
    def index(self):
        return "Root"            

def reverse(cls):
    #return cherrypy.tree.apps.keys()
    #return dir(cherrypy.tree.apps[''].root)
    #return dir(cherrypy.tree.apps['/page3/apple'].root)
    # get link to apple
    for app_url in cherrypy.tree.apps.keys():
        if isinstance(cherrypy.tree.apps[app_url].root, cls):
            # NOTE: it will return with the first instance
            return app_url

root = Root()
root.page1 = Page1()
root.page1.apple = Apple()
root.page2 = Page2()
root.page2.orange = Orange()

cherrypy.tree.mount(root, '/')
# if you do not specify the mount points you can find the objects
# in cherrypy.tree.apps[''].root...
cherrypy.tree.mount(root.page1, '/page4')
cherrypy.tree.mount(root.page2, '/page3')
cherrypy.tree.mount(root.page2.orange, '/page4/orange')
cherrypy.tree.mount(root.page1.apple, '/page3/apple')

link_to_apple_global = reverse(Apple)

cherrypy.engine.start()
cherrypy.engine.block()